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Lack of Exercise Is a Major Cause of Chronic Diseases

  1. Frank W. Booth1,
  2. Christian K. Roberts2,
  3. Matthew J. Laye3

Published Online: 1 APR 2012

DOI: 10.1002/cphy.c110025

Comprehensive Physiology

Comprehensive Physiology

How to Cite

Booth, F. W., Roberts, C. K. and Laye, M. J. 2012. Lack of Exercise Is a Major Cause of Chronic Diseases. Comprehensive Physiology. 2:1143–1211.

Author Information

  1. 1

    Departments of Biomedical Sciences, Medical Pharmacology and Physiology, and Nutrition and Exercise Physiology, Dalton Cardiovascular Institute, University of Missouri, Columbia, Missouri

  2. 2

    School of Nursing and Center for Metabolic Disease Prevention, University of California, Los Angeles, California

  3. 3

    Centre of Inflammation and Metabolism, Copenhagen, Denmark and Buck Institute for Research on Aging, Novato, California

Publication History

  1. Published Online: 1 APR 2012

1 Organization of Article

  1. Top of page
  2. Organization of Article
  3. Definitions
  4. Overview for Next Three Sections
  5. Summary of Daily Step Reductions from Antiquity
  6. History of Inactivity's Compromising Effects on Function and Health
  7. Cause Versus Treatment
  8. Mechanisms of Physical Inactivity and Activity Differ
  9. Gene-Exercise/Physical Inactivity Interactions
  10. Twin Studies: Modulation of Twin Phenotype by Physical Activity
  11. Variety of Training Types to Primarily Prevent Disease
  12. Diseasome of Physical Inactivity (35 Diseases/Conditions)
  13. Inactivity Accelerates Loss of Functional Capacities with Years of Life
  14. Prevention of Death by Primary Prevention of Physical Inactivity
  15. Metabolic Syndrome
  16. Presentation Strategy for Diseases Composing MS
  17. Obesity
  18. Inactivity Fosters Obese Comorbidities
  19. Insulin Sensitivity/Resistance
  20. Prediabetes
  21. Type 2 Diabetes
  22. Nonalcoholic Fatty Liver Disease
  23. Cardiovascular Diseases: All Types
  24. Presentation of Individual Cardiovascular Diseases
  25. Coronary Heart Disease
  26. Peripheral Arterial Disease
  27. Hypertension
  28. Stroke
  29. Congestive Heart Failure
  30. Known Mechanisms for CVD Risk Factors
  31. Deep Vein Thrombosis
  32. Cognitive Function
  33. Depression and Anxiety
  34. Bone (Osteoporosis)
  35. Osteoarthritis
  36. Balance
  37. Rheumatoid Arthritis
  38. Cancer
  39. Colon Cancer
  40. Breast Cancer
  41. Endometrial Cancer
  42. Activity Prevention of Female Reproductive Disorders
  43. Activity Prevention of Male Reproductive Disorders
  44. Pain
  45. Digestive Tract Diseases
  46. Chronic Respiratory Diseases
  47. Chronic Kidney Disease
  48. Clinical Significance of Physical Inactivity as One Cause of 35 Chronic Conditions
  49. Effectiveness of Drug Therapy for Simultaneous Primary Prevention of 35 Physical Inactivity Conditions
  50. Risk Factors Worsen Over 6 to 12 Months in RCTs
  51. Primary Prevention of Physical Inactivity: Childhood Developing Adult Disorders
  52. Public Policy
  53. Conclusion
  54. Acknowledgements
  55. References

1.1 Entire article

An underappreciated primary cause of most chronic conditions is the lack of sufficient daily physical activity (physical inactivity). Overwhelming evidence proves the notion that reductions in daily physical activity are primary causes of chronic diseases/conditions and that physical activity/exercise is rehabilitative treatment (therapy) from the inactivity-caused dysfunctions. The general strategy of presentation divides the article into three major sections: (i) conceptual information forming the foundation to understand the remaining article, (ii) primary literature supporting physical inactivity as a primary cause to a myriad of chronic conditions/diseases, and (iii) additional considerations. The aim of the entire article is to bring better understanding and insight into the observation that a lack of physical activity at ancestral levels initiates 35 pathological and clinical conditions.

1.2 First third of article

Conceptual information is presented in five parts in the first third portion of the article: (i) definitions of forms of physical activity, functional capacity, types of fitness, chronic diseases, and types of prevention so that the reader understands how the article employs these words; (ii) a brief chronology of the three-millennia history that recognizes that physical inactivity reduces functional capacity and health; (iii) cause versus treatment is discussed to emphasize that physical inactivity is a primary cause of chronic conditions/diseases; (iv) growing evidence that mechanisms by which inactivity causes disease differ from mechanisms by which physical activity is a therapy/treatment to act as a primary preventer of disease; and (v) gene-environment interactions have varying degrees of gene involvement in the magnitude of change to physical activity.

1.3 Center portion of article

Physical inactivity is a primary cause initiating 35 separate pathological and clinical conditions. Many of the 35 conditions are subdivided under major categories, such as loss of functional capacities with chronological aging; metabolic syndrome, obesity, insulin resistance, prediabetes/type 2 diabetes (T2D), nonalcoholic liver disease, cardiovascular diseases (CVDs), cognitive functions and diseases, bone and connective tissue disorders, cancer, reproductive diseases, and diseases of digestive tract, pulmonary, and kidney.

1.4 Final portion of article

The article ends with considerations of clinical significance, increasing risk factors during long-term sedentarism, the developmental and clinical consequences of inactive childhood/adolescence, and policy.

2 Definitions

  1. Top of page
  2. Organization of Article
  3. Definitions
  4. Overview for Next Three Sections
  5. Summary of Daily Step Reductions from Antiquity
  6. History of Inactivity's Compromising Effects on Function and Health
  7. Cause Versus Treatment
  8. Mechanisms of Physical Inactivity and Activity Differ
  9. Gene-Exercise/Physical Inactivity Interactions
  10. Twin Studies: Modulation of Twin Phenotype by Physical Activity
  11. Variety of Training Types to Primarily Prevent Disease
  12. Diseasome of Physical Inactivity (35 Diseases/Conditions)
  13. Inactivity Accelerates Loss of Functional Capacities with Years of Life
  14. Prevention of Death by Primary Prevention of Physical Inactivity
  15. Metabolic Syndrome
  16. Presentation Strategy for Diseases Composing MS
  17. Obesity
  18. Inactivity Fosters Obese Comorbidities
  19. Insulin Sensitivity/Resistance
  20. Prediabetes
  21. Type 2 Diabetes
  22. Nonalcoholic Fatty Liver Disease
  23. Cardiovascular Diseases: All Types
  24. Presentation of Individual Cardiovascular Diseases
  25. Coronary Heart Disease
  26. Peripheral Arterial Disease
  27. Hypertension
  28. Stroke
  29. Congestive Heart Failure
  30. Known Mechanisms for CVD Risk Factors
  31. Deep Vein Thrombosis
  32. Cognitive Function
  33. Depression and Anxiety
  34. Bone (Osteoporosis)
  35. Osteoarthritis
  36. Balance
  37. Rheumatoid Arthritis
  38. Cancer
  39. Colon Cancer
  40. Breast Cancer
  41. Endometrial Cancer
  42. Activity Prevention of Female Reproductive Disorders
  43. Activity Prevention of Male Reproductive Disorders
  44. Pain
  45. Digestive Tract Diseases
  46. Chronic Respiratory Diseases
  47. Chronic Kidney Disease
  48. Clinical Significance of Physical Inactivity as One Cause of 35 Chronic Conditions
  49. Effectiveness of Drug Therapy for Simultaneous Primary Prevention of 35 Physical Inactivity Conditions
  50. Risk Factors Worsen Over 6 to 12 Months in RCTs
  51. Primary Prevention of Physical Inactivity: Childhood Developing Adult Disorders
  52. Public Policy
  53. Conclusion
  54. Acknowledgements
  55. References

2.1 CDC definitions of forms of physical activity

Verbatim definitions for exercise and health are from the US Centers for Disease Control and Prevention (CDC) are used where possible due to the authority they carry 90. US governmental definitions were selected for the article to provide the framework for this article's discussions of how (i) exercise/physical activity prevents chronic diseases and (ii) lack of physical activity is a primary event that causes chronic diseases.

2.1.1 Exercise

“A subcategory of physical activity that is planned, structured, repetitive, and purposive in the sense that the improvement or maintenance of one or more components of physical fitness is the objective,” as defined by CDC 90.

2.1.2 Exercise training

“Physical activity performed during leisure time with the primary purpose of improving or maintaining physical fitness, physical performance, or health,” as defined by CDC 90.

2.1.3 Physical activity

“Any bodily movement produced by the contraction of skeletal muscle that increases energy expenditure above a basal level. Physical activity generally refers to the subset of physical activity that enhances health,” as defined by CDC 90.

2.1.4 Health

“A human condition with physical, social, and psychological dimensions, each characterized on a continuum with positive and negative poles,” as defined by CDC 90.

2.1.5 Health-enhancing physical activity

“Activity that, when added to baseline activity, produces health benefits. Brisk walking, jumping rope, dancing, playing tennis or soccer, lifting weights, climbing on playground equipment at recess, and doing yoga are all examples of health-enhancing physical activity,” as defined by CDC 90.

As previously stated, this article will concentrate on the use of physical activity to prevent physical inactivity, and thus, prevent many chronic diseases.

2.2 Definition of physical inactivity

CDC definitions for exercise do not include a definition of “physical inactivity.” We define physical inactivity as “physical activity levels less than those required for optimal health and prevention of premature death.” Further consideration of the definition is given in Section “Prevention of Death by Primary Prevention of Physical Inactivity.”

2.3 Definition of functional capacity

We define “functional capacity” as the ability of a cell, organ, system, or body to maintain homeostasis within their narrow limits of survival in response to a specified stress. If an external stress disrupts homeostasis beyond an organism's functional capacity, life may not be sustained. Diminished ability to adapt to stressors increases the likelihood of death. Functional capacity is pliable; declining rapidly with extreme physical inactivity or more slowly with aging, while preventing inactivity can increase functional capacity (considered in specific detail in the aging section). Importantly, a direct relationship between functional capacity and survival is a cornerstone of general medicine theory. A major predictor of functional capacity is maximal aerobic capacity (Vo2max), which while directly testing cardiovascular fitness and integrity also represents a combination of other physiologic components. For instance, Vo2max also depends on pulmonary and muscle function, health status of other organ systems, nutritional status, medications, orthopedic limitations, and others 351. An aerobic functional capacity in patients under 4-metabolic equivalents (METs), a typical demand during normal daily activities, increases postoperative (time from admission to discharge from surgery) cardiac and long-term risks 155. In another study, patients were grouped by MET capacity in relationship to complication prevalence after they underwent angiographically verified coronary artery disease and subsequent open abdominal nonvascular surgery 264. Those from the group less than 4 METs had cardiologic complications in 64% of cases, the 4 to 7 METs group had 29%, and the 7 to 10 METs group had 8%. These remarkable findings can be extrapolated to other stresses where the probability of complications, and even survival, is dependent upon the functional capacity needed to maintain homeostasis.

2.4 Physical fitness versus physical activity

Some people incorrectly use physical fitness and physical activity interchangeably. The CDC defines physical fitness as:

“The ability to carry out daily tasks with vigor and alertness, without undue fatigue, and with ample energy to enjoy leisure-time pursuits and respond to emergencies. Physical fitness includes a number of components consisting of cardiorespiratory endurance (aerobic power), skeletal muscle endurance, skeletal muscle strength, skeletal muscle power, flexibility, balance, speed of movement, reaction time, and body composition.”

The CDC defines physical activity as “Any bodily movement produced by the contraction of skeletal muscle that increases energy expenditure above a basal level” 90.

Inherited genes and their interaction with physical activity levels determine physical fitness. However, chronic physical activity levels themselves modulate fitness. Further, the levels of physical activity, themselves, modulate whether fitness improves. For example, Sisson et al. 477 concluded that the most important finding of their study was that greater volumes of exercise were associated with a lower probability of being a nonresponder. The percentage of nonresponders at a given level of training progressively decreased as the exercise volume increased.

2.5 Cardiorespiratory fitness

We define cardiorespiratory fitness (CRF) as the capacity of the cardiovascular (heart and blood vessels) and respiratory (lungs) systems to supply oxygen-rich blood to the working skeletal muscles and the capacity of the muscles to use oxygen to produce energy for movement. The gold standard to determine CRF is the aforementioned Vo2max, or maximum aerobic fitness. However, in large clinical human studies, an acceptable surrogate for Vo2max is the length of time running or cycling in standardized test, assuming appropriate physiological/biochemical/psychological proof of exhaustion is obtained 65, 262.

The majority of data about fitness and physical activity is focused on aerobic fitness. Data indicate that rapid, severe physical inactivity can rapidly decrease CRF. For instance, in the Dallas Bed Rest study, healthy, young males’ Vo2max decreased 27% after 20 days of continuous bed rest 453 and another study in Denmark 2 weeks of reducing daily step number from 10,501 to 1344 Vo2max decreased 7% 388.

2.6 Strength fitness

We define strength fitness as the capacity of the skeletal muscle to move an external load. Strength is highly dependent upon skeletal muscle mass, which contains a major genetic component (discussed later in Section “Twin Studies: Modulation of Twin Health by Physical Activity”), and is sensitive to decreased mechanical loading resulting in skeletal muscle atrophy regardless of endowed muscle mass 49, 507.

2.7 Balance and flexibility fitness

We define balance fitness as the ability to control the body's position throughout movement, and flexibility fitness as the ability to achieve an extended range of motion. Both have components of genetic inheritability and are also trainable (discussed later in Section “Twin Studies: Modulation of Twin Health by Physical Activity”).

2.8 Definition of chronic diseases and their prevalence

We define chronic disease as a disease slow in its progress (decades) and long in its continuance, as opposed to acute disease, which is characterized by a swift onset and short course.

Medicine, public health, pharmaceutical industry, and educational systems have reduced infectious diseases and early life mortality resulting in record average life spans for much of the human population. In place of infectious diseases, most people in the United States now die of chronic diseases.

The CDC Website states:

“Chronic diseases—such as heart disease, cancer, and diabetes—are the leading causes of death and disability in the United States. Chronic diseases account for 70% of all deaths in the United States, which is 1.7 million each year (87). These diseases also cause major limitations in daily living for almost 1 of 10 Americans or about 25 million people (87).”

The CDC further wrote, “Chronic diseases—such as heart disease, stroke, cancer, diabetes, and arthritis—are among the most common, costly, and preventable of all health problems in the United States” 85. In addition to the CDC, former US Secretary of Health and Human Services, the Honorable Michael O. Leavitt in the 2008 Physical Activity Guidelines for Americans, wrote:

“Along with President Bush, I believe that physical activity should be an essential component of any comprehensive disease prevention and health promotion strategy for Americans. We know that sedentary behavior contributes to a host of chronic diseases, and regular physical activity is an important component of an overall healthy lifestyle. There is strong evidence that physically active people have better health-related physical fitness and are at lower risk of developing many disabling medical conditions than inactive people 531.”

2.9 Definitions of types of prevention

For the purposes of this article, physical activity is presented as primary prevention of physical inactivity. The CDC defines physical inactivity as an actual cause of chronic conditions 212, 344. Physical activity, itself, rarely causes chronic conditions, for example, participation in specific sports improves general health, but can increase the risk of osteoarthritis (OA) in specific populations 71; discussed later in Section “Osteoarthritis.” The next definitions are taken from a commissioned paper by the US Institute of Medicine 266.

2.9.1 Prevent

Prevent implies taking advanced measures against something possible or probable. Prevention in medicine has been divided into three progressive stages—primary, secondary, and tertiary 266.

2.9.1.1 Primary prevention

“Primary prevention refers to health promotion, which fosters wellness in general and thus reduces the likelihood of disease, disability, and premature death in a nonspecific manner, as well as specific protection against the inception of disease” 266.

2.9.1.2 Secondary prevention

“Secondary prevention refers to the detection and management of presymptomatic disease, and the prevention of its progression to symptomatic disease. Screening is the dominant practice. The margins between primary and secondary prevention can at times blur 267. For example, if hypertension is defined as a disease, its treatment is secondary prevention; if defined as a risk factor for coronary disease that does not yet exist, it is primary prevention” 266.

2.9.1.3 Tertiary prevention

“Tertiary prevention refers to the treatment of symptomatic disease in an effort to slowdown its further progression to disability or premature death. There is a legitimate focus on prevention even after disease develops, such as the prevention of early cancer from metastasizing, or the prevention of coronary disease from inducing a myocardial infarction or heart failure. This domain also encompasses rehabilitation, the purpose of which is to preserve or restore functional ability, and thus prevent its degeneration 266.”

2.10 Application of exercise to prevention categories

Examples for our view that exercise is a primary, secondary, and tertiary preventer of disease are as follows: (i) primary prevention (direct treatment of cause to prevent disease occurrence) is voluntary avoidance of physical inactivity or treatment of physical inactivity with physical activity; (ii) secondary treatment [eliminating one cause (physical inactivity) of existing hypertension by eliminating physical inactivity] is treatment of existing hypertension with physical activity; and (iii) tertiary prevention with physical activity is cardiac rehabilitation where exercise benefits do not reverse the anatomical pathology from myocardial infarction. We propose that the greatest health benefit of physical activity is primary prevention of 35 chronic diseases/conditions to become clinically overt. This article is largely restricted to consideration of primary prevention of inactivity as an actual cause of chronic conditions.

3 Overview for Next Three Sections

  1. Top of page
  2. Organization of Article
  3. Definitions
  4. Overview for Next Three Sections
  5. Summary of Daily Step Reductions from Antiquity
  6. History of Inactivity's Compromising Effects on Function and Health
  7. Cause Versus Treatment
  8. Mechanisms of Physical Inactivity and Activity Differ
  9. Gene-Exercise/Physical Inactivity Interactions
  10. Twin Studies: Modulation of Twin Phenotype by Physical Activity
  11. Variety of Training Types to Primarily Prevent Disease
  12. Diseasome of Physical Inactivity (35 Diseases/Conditions)
  13. Inactivity Accelerates Loss of Functional Capacities with Years of Life
  14. Prevention of Death by Primary Prevention of Physical Inactivity
  15. Metabolic Syndrome
  16. Presentation Strategy for Diseases Composing MS
  17. Obesity
  18. Inactivity Fosters Obese Comorbidities
  19. Insulin Sensitivity/Resistance
  20. Prediabetes
  21. Type 2 Diabetes
  22. Nonalcoholic Fatty Liver Disease
  23. Cardiovascular Diseases: All Types
  24. Presentation of Individual Cardiovascular Diseases
  25. Coronary Heart Disease
  26. Peripheral Arterial Disease
  27. Hypertension
  28. Stroke
  29. Congestive Heart Failure
  30. Known Mechanisms for CVD Risk Factors
  31. Deep Vein Thrombosis
  32. Cognitive Function
  33. Depression and Anxiety
  34. Bone (Osteoporosis)
  35. Osteoarthritis
  36. Balance
  37. Rheumatoid Arthritis
  38. Cancer
  39. Colon Cancer
  40. Breast Cancer
  41. Endometrial Cancer
  42. Activity Prevention of Female Reproductive Disorders
  43. Activity Prevention of Male Reproductive Disorders
  44. Pain
  45. Digestive Tract Diseases
  46. Chronic Respiratory Diseases
  47. Chronic Kidney Disease
  48. Clinical Significance of Physical Inactivity as One Cause of 35 Chronic Conditions
  49. Effectiveness of Drug Therapy for Simultaneous Primary Prevention of 35 Physical Inactivity Conditions
  50. Risk Factors Worsen Over 6 to 12 Months in RCTs
  51. Primary Prevention of Physical Inactivity: Childhood Developing Adult Disorders
  52. Public Policy
  53. Conclusion
  54. Acknowledgements
  55. References

While, concerns that physical inactivity is detrimental to health have been documented for over three millennia, much remains unknown, for example, (i) how to change the sedentary behavior of the 92% of US adolescents and more than 95% of adults who do not met the US Department of Health and Human Services guidelines for physical activity 526, (ii) how to have health care professionals provide effective individualized exercise prescriptions, and (iii) what are the molecular links between inactivity and chronic disease that will provide a policy tool in the same way as the molecular link between the carcinogen in tobacco and lung cancer did 129.

4 Summary of Daily Step Reductions from Antiquity

  1. Top of page
  2. Organization of Article
  3. Definitions
  4. Overview for Next Three Sections
  5. Summary of Daily Step Reductions from Antiquity
  6. History of Inactivity's Compromising Effects on Function and Health
  7. Cause Versus Treatment
  8. Mechanisms of Physical Inactivity and Activity Differ
  9. Gene-Exercise/Physical Inactivity Interactions
  10. Twin Studies: Modulation of Twin Phenotype by Physical Activity
  11. Variety of Training Types to Primarily Prevent Disease
  12. Diseasome of Physical Inactivity (35 Diseases/Conditions)
  13. Inactivity Accelerates Loss of Functional Capacities with Years of Life
  14. Prevention of Death by Primary Prevention of Physical Inactivity
  15. Metabolic Syndrome
  16. Presentation Strategy for Diseases Composing MS
  17. Obesity
  18. Inactivity Fosters Obese Comorbidities
  19. Insulin Sensitivity/Resistance
  20. Prediabetes
  21. Type 2 Diabetes
  22. Nonalcoholic Fatty Liver Disease
  23. Cardiovascular Diseases: All Types
  24. Presentation of Individual Cardiovascular Diseases
  25. Coronary Heart Disease
  26. Peripheral Arterial Disease
  27. Hypertension
  28. Stroke
  29. Congestive Heart Failure
  30. Known Mechanisms for CVD Risk Factors
  31. Deep Vein Thrombosis
  32. Cognitive Function
  33. Depression and Anxiety
  34. Bone (Osteoporosis)
  35. Osteoarthritis
  36. Balance
  37. Rheumatoid Arthritis
  38. Cancer
  39. Colon Cancer
  40. Breast Cancer
  41. Endometrial Cancer
  42. Activity Prevention of Female Reproductive Disorders
  43. Activity Prevention of Male Reproductive Disorders
  44. Pain
  45. Digestive Tract Diseases
  46. Chronic Respiratory Diseases
  47. Chronic Kidney Disease
  48. Clinical Significance of Physical Inactivity as One Cause of 35 Chronic Conditions
  49. Effectiveness of Drug Therapy for Simultaneous Primary Prevention of 35 Physical Inactivity Conditions
  50. Risk Factors Worsen Over 6 to 12 Months in RCTs
  51. Primary Prevention of Physical Inactivity: Childhood Developing Adult Disorders
  52. Public Policy
  53. Conclusion
  54. Acknowledgements
  55. References

Historical evidence shows that physical inactivity is prevalent in today's society relative to historical levels 384. Estimated daily step numbers have declined approximately 50% to 70% since the introduction of powered machinery (Table 1).

Table 1. Estimated Historical Reductions in Daily Steps By Humans
Population yearSteps per dayReferences
Paleolithic (∼20,000 BC)∼13,200-21,120 (men); ∼10,560 (women)384
Amish (2002)18,425 (men); 14,196 (women)27
Mean of 26 studies (1966-2007)7473 (mainly women)63
Colorado (2002)6733 (men); 6384 (women)572
US adults (2010)5340 (men); 4912 (women)26

5 History of Inactivity's Compromising Effects on Function and Health

  1. Top of page
  2. Organization of Article
  3. Definitions
  4. Overview for Next Three Sections
  5. Summary of Daily Step Reductions from Antiquity
  6. History of Inactivity's Compromising Effects on Function and Health
  7. Cause Versus Treatment
  8. Mechanisms of Physical Inactivity and Activity Differ
  9. Gene-Exercise/Physical Inactivity Interactions
  10. Twin Studies: Modulation of Twin Phenotype by Physical Activity
  11. Variety of Training Types to Primarily Prevent Disease
  12. Diseasome of Physical Inactivity (35 Diseases/Conditions)
  13. Inactivity Accelerates Loss of Functional Capacities with Years of Life
  14. Prevention of Death by Primary Prevention of Physical Inactivity
  15. Metabolic Syndrome
  16. Presentation Strategy for Diseases Composing MS
  17. Obesity
  18. Inactivity Fosters Obese Comorbidities
  19. Insulin Sensitivity/Resistance
  20. Prediabetes
  21. Type 2 Diabetes
  22. Nonalcoholic Fatty Liver Disease
  23. Cardiovascular Diseases: All Types
  24. Presentation of Individual Cardiovascular Diseases
  25. Coronary Heart Disease
  26. Peripheral Arterial Disease
  27. Hypertension
  28. Stroke
  29. Congestive Heart Failure
  30. Known Mechanisms for CVD Risk Factors
  31. Deep Vein Thrombosis
  32. Cognitive Function
  33. Depression and Anxiety
  34. Bone (Osteoporosis)
  35. Osteoarthritis
  36. Balance
  37. Rheumatoid Arthritis
  38. Cancer
  39. Colon Cancer
  40. Breast Cancer
  41. Endometrial Cancer
  42. Activity Prevention of Female Reproductive Disorders
  43. Activity Prevention of Male Reproductive Disorders
  44. Pain
  45. Digestive Tract Diseases
  46. Chronic Respiratory Diseases
  47. Chronic Kidney Disease
  48. Clinical Significance of Physical Inactivity as One Cause of 35 Chronic Conditions
  49. Effectiveness of Drug Therapy for Simultaneous Primary Prevention of 35 Physical Inactivity Conditions
  50. Risk Factors Worsen Over 6 to 12 Months in RCTs
  51. Primary Prevention of Physical Inactivity: Childhood Developing Adult Disorders
  52. Public Policy
  53. Conclusion
  54. Acknowledgements
  55. References

Three millennia of evidence exist to indicate historical recognition that physical inactivity is detrimental to health by reducing the functional capacity of most organ systems in humans, mammals, and rodents.

5.1 Ancient India (∼ 1500-600 BC)

A historical review by Tipton 518 described the tridosa doctrine in India, which contended that the three humors regulated all functions of the body. When humors were in equilibrium, good health was present. However, sedentary living and lack of exercise could displace one or more of the humors, impairing health and potentially leading to illness and death. Susruta (600 BC) was convinced a sedentary lifestyle elevate the kapha humor to a level that could disrupt humoral equilibrium resulting in a disease state and potential death. He included exercise in his recommendations to prevent the occurrence of diseases.

5.2 Hippocrates (∼ 450 BC)

Quotations attributed to Hippocrates promote the primary prevention of disease by physical activity:

“If we could give every individual the right amount of nourishment and exercise, not too little and not too much, we would have found the safest way to health 239.”

“If there is any deficiency in food and exercise the body will fall sick 476.”

“Walking is man's best medicine 239.”

“All parts of the body, if used in moderation and exercised in labors to which each is accustomed, become thereby healthy and well developed and age slowly; but if they are unused and left idle, they become liable to disease, defective in growth and age quickly 277.”

5.3 Bed rest (1945-1955)

Three days of physical inactivity produces glucose intolerance 47. Paul Dudley White, one of Dwight Eisenhower's cardiologists after the President's heart attack on September 24, 1955, prescribed physical activity to President Eisenhower long before the end of the standard treatment of 6-month bed rest for a heart attack. The medical community followed White's practice of substituting physical activity for bed rest in management of acute coronary syndromes, with bed durations progressively decreasing to 2 weeks in 1980 to 2005 339. A 2011 meta-analysis concludes that exercise training has greatest beneficial effects on left ventricular (LV) remodeling in clinically stable post-myocardial infarction (MI) patients when training starts 1 week following the MI 226.

5.4 Initial epidemiology (1949-1953)

Jeremiah Morris is recognized as the person who first used physical activity in epidemiology (his history is available at reference 43. In 1953, Morris and co-workers compared bus drivers, who are sedentary in their occupation, with the physically active bus conductors, who were constantly moving up and down double-decker buses to collect fares in London. Physically active conductors had a 30% lower incidence rate of coronary heart disease (CHD) than the physically inactive bus drivers 352. Furthermore, even the physically active conductors who did develop CHD with age were better off, presenting with less severe disease and lower fatality rates than the inactive bus drivers 352. However, while Vo2max was not determined in Morris’ report, others have since shown that workers in physically active occupations have higher aerobic capacity than their inactive peers 219. Morris’ 1953 report 352 is a milestone as the initial publication documenting daily physical inactivity is associated with increased morbidity and mortality 43.

In his tenth decade of Morris’ life, he wrote, “We in the West are the first generation in human history in which the mass of the population has to deliberately exercise to be healthy. How can society's collective adaptations match?” 43, 353.

5.5 Primary prevention: Human space flight (1957-1961)

The Space Race for national security began in earnest in 1954 leading to the successful launch and orbit of Sputnik from the USSR on October 4, 1957. Four years later on April 12, 1961, Yuri Gagarin became the first human in outer space and the first to orbit the Earth. The Space Race hastened physiological exploration that the microgravity experienced in space reduced human functional capacities. As an outcome, NASA researched countermeasures to the microgravity-induced functional loss during space flight that relied on experimental bed rest on Earth, an extreme form of inactivity. However, interest in the primary mechanisms of inactivity was a lower priority.

Today, over 6500 publications arise from a PubMed search for the terms space flight and physiology. Inspection of this body of literature led Vernikos and Schneider 539 to contend that space flight results in losses of functional capacities in multiple organ systems, similar to an accelerated model-mimicking aging. For example, they conclude that bone atrophy occurs ten times faster in space flight than with aging. Similarly, reductions in immune function, sensitivity of arterial baroreflex, maximal stroke volume, maximal cardiac output, and Vo2max also occur more rapidly in space flight than in aging 539, 560.

5.6 Bed rest book (1965)

The preface of Browse's book “The Physiology and Pathology of Bed Rest,” published in 1965 states that the principle purpose of the book:

“…is to lay bare our ignorance of the whole subject, to stimulate research. The dangers of bed rest are so many, and in some cases so final, that we should always be striving to discard it from our therapeutic armamentarium…and to emphasize the absurdity of using a nonspecific treatment for specific diseases without reason or proven value 68.”

The book carefully documents the widespread systemic deterioration of the body when continuous bed rest occurs. Some of the pathologies documented are: postural hypotension, tachycardia, kidney stones (renal calculi), loss of skeletal muscle mass, weakness in antigravity muscles, pressure ulcers, osteoporosis, constipation, deep vein thrombosis, pulmonary embolism, pneumonia, and difficulty with micturition.

5.7 Dallas bed rest study (1960s)

Saltin et al. 453 studied five healthy college-age males during 20 days of continuous bed rest. During acute exercise following bed rest reductions of 28%, 11%, 26%, and 29% in Vo2max, ventricular volume (mL), maximal cardiac output, and maximal stroke volume occurred, without a change in maximal A-Vo2 difference. Further detrimental changes with bed rest were increased heart rate at a submaximal workload of 600 kpm/min from 129 to 154 beats/min and total peripheral resistance (TPR) increasing from 449 to 520 TPR units. From the 10th to 20th day of bed rest, heart rate increased from 47 to 51 beats/min.

5.8 Sitting studies (2000s)

A perspective was proposed as to whether too much sitting is distinct from too little exercise 217, 316, 391, 392. Owen et al.'s 2010 review states:

“Further evidence from prospective studies, intervention trials, and population-based behavioral studies is required…many scientific questions remain to be answered before it can be concluded with a high degree of certainty that these adverse health consequences are uniquely caused by too much sitting, or if what has been observed so far can be accounted for by too little light, moderate, and/or vigorous activity 391.”

A 2010 review coauthored from multiple research sites concluded from an examination of 43 papers, “Limited evidence was found to support a positive relationship between occupational sitting and health risks. The heterogeneity of study designs, measures, and findings makes it difficult to draw definitive conclusions at this time” 536. The concept of intermittency of lack of weight bearing by sitting is supported by older basic science research. In rats, cycling 4 times per day through periods of weight bearing and nonweight bearing (hind limb suspension), soleus muscle atrophy was prevented by 4 × 15-min periods of ground support during 12 h of the day 118.

5.9 Animal wheel lock studies (2000s)

To optimize primary prevention by physical activity, mechanisms by which physical inactivity initiates risk factors for chronic diseases must be elucidated for the optimal science-based physical activity prescription. One animal model used young male rats that underwent 3 weeks of voluntary running and then had their wheels locked (WL) for 5 h (WL5), 29 h (WL29), or 53 h (WL53). Within 53 h, two major changes in functional capacities were observed, decreased submaximal insulin sensitivity and enhanced storage of triglycerides (TG) in visceral adipose tissue (VAT). (For the purposes of this article, visceral and intra-abdominal adipose tissues are considered similar and the term visceral is used). Specifically, submaximal insulin-stimulated 2-deoxyglucose uptake, insulin binding, insulin receptor ß-subunit (IRß) protein level, submaximal insulin-stimulated IRß tyrosine phosphorylation, glucose transporter-4 protein level, and Akt/protein kinase B Ser473 phosphorylation (an index of proximal insulin signaling) in the epitrochlearis muscle, returned to sedentary levels at WL53 292. Further, the epididymal adipose tissue mass at WL53 weighed 25% more than at WL5 in the same rats as studied for insulin sensitivity previously.

5.10 Translation studies: Reduced stepping studies in humans (2000s)

While continuous bed rest is a model examining the absence of physical activity, a novel human reduced-activity model was designed to test the effects of reduced, rather than lack of, physical activity on metabolic health. Step numbers were reduced by taking elevators instead of stairs and riding in cars instead of walking or bicycling within a free-living environment by young, healthy male adults who were not undertaking more than 2 h/week exercise at the start of the study. After reducing daily step number form 6203 to 1394 for 3 weeks, areas under the curve (AUC) for plasma insulin during an oral glucose tolerance test (OGTT) progressively increased 53%, 61%, and 79% after 1, 2, and 3 weeks, respectively 388.

In a second study, subjects reduced daily steps from 10,501 to 1344 (where there are ∼ 2000 steps in a mile). After 2 weeks, Vo2max decreased 7%, peripheral insulin sensitivity decreased by 17% with concurrent decreases in insulin-stimulated ratio of pAkt-Thr308/total Akt in skeletal muscle. Body composition was also significantly altered by 2 weeks of reduced stepping with VAT mass increased 7%, total fat-free mass decreased by 1.2 kg, 0.5 kg of it in the legs, while total-body fat mass and body mass index (BMI) were unchanged 285, 388. Thus, an inverse relationship existed between gain of VAT and loss of lean mass, indicative of body composition repartitioning. Similar observations have been made in a rat WL model. In a different WL experiment VAT mass, but not lean mass increased independent of food intake after 173 h of WL followed 6 weeks of voluntary running 309. Thus, both human and rat models of reduced daily steps increased VAT while diminishing lean mass, independent of caloric increases.

5.11 Clinical significance

Short-term reductions in daily step number (producing less daily physical activity) cause decreased CRF, loss of insulin sensitivity, reduced lean mass, and increased VAT. These functional decrements help explain the link between reduced physical activity and the risks that have been associated with the progression of chronic disorders and premature mortality 388. Using physical activity prescriptions to prevent physical inactivity would help maintain functional capacities.

5.12 Summary: Inactivity causes loss of functional capacities

Taken together, the historical work provides overwhelming evidence that physical inactivity causes decreases in capacities of functional systems, leading to premature deterioration of health in humans. The Copenhagen study of reduced stepping, while low in subject number, is particularly relevant to everyday living because the reduced physical activity level is similar to the step numbers performed in a free-living environment by billions of humans worldwide in both developed and developing countries.

6 Cause Versus Treatment

  1. Top of page
  2. Organization of Article
  3. Definitions
  4. Overview for Next Three Sections
  5. Summary of Daily Step Reductions from Antiquity
  6. History of Inactivity's Compromising Effects on Function and Health
  7. Cause Versus Treatment
  8. Mechanisms of Physical Inactivity and Activity Differ
  9. Gene-Exercise/Physical Inactivity Interactions
  10. Twin Studies: Modulation of Twin Phenotype by Physical Activity
  11. Variety of Training Types to Primarily Prevent Disease
  12. Diseasome of Physical Inactivity (35 Diseases/Conditions)
  13. Inactivity Accelerates Loss of Functional Capacities with Years of Life
  14. Prevention of Death by Primary Prevention of Physical Inactivity
  15. Metabolic Syndrome
  16. Presentation Strategy for Diseases Composing MS
  17. Obesity
  18. Inactivity Fosters Obese Comorbidities
  19. Insulin Sensitivity/Resistance
  20. Prediabetes
  21. Type 2 Diabetes
  22. Nonalcoholic Fatty Liver Disease
  23. Cardiovascular Diseases: All Types
  24. Presentation of Individual Cardiovascular Diseases
  25. Coronary Heart Disease
  26. Peripheral Arterial Disease
  27. Hypertension
  28. Stroke
  29. Congestive Heart Failure
  30. Known Mechanisms for CVD Risk Factors
  31. Deep Vein Thrombosis
  32. Cognitive Function
  33. Depression and Anxiety
  34. Bone (Osteoporosis)
  35. Osteoarthritis
  36. Balance
  37. Rheumatoid Arthritis
  38. Cancer
  39. Colon Cancer
  40. Breast Cancer
  41. Endometrial Cancer
  42. Activity Prevention of Female Reproductive Disorders
  43. Activity Prevention of Male Reproductive Disorders
  44. Pain
  45. Digestive Tract Diseases
  46. Chronic Respiratory Diseases
  47. Chronic Kidney Disease
  48. Clinical Significance of Physical Inactivity as One Cause of 35 Chronic Conditions
  49. Effectiveness of Drug Therapy for Simultaneous Primary Prevention of 35 Physical Inactivity Conditions
  50. Risk Factors Worsen Over 6 to 12 Months in RCTs
  51. Primary Prevention of Physical Inactivity: Childhood Developing Adult Disorders
  52. Public Policy
  53. Conclusion
  54. Acknowledgements
  55. References

“A sedentary lifestyle over several years is associated with increased risk for type 2 diabetes, cardiovascular disease, and premature mortality. What is much less appreciated is the high cost of physical inactivity even in the short term. Booth et al. have been drawing attention for years to the societal and individual burden of inactivity-related chronic diseases. They remind us that while exercise is a treatment to prevent many chronic diseases, it is the lack of regular exercise or physical inactivity that is one of the actual causes of many of these diseases 480.”

Convincing proof that physical inactivity causes primary deterioration of function is provided from extensive historical and scientific evidence. Thus, physical activity can prevent physical inactivity-induced chronic diseases (left panel of Fig. 1). In contrast (right panel of Fig. 1), physical activity can treat against lung cancer-induced dyspnea, a common side effect 1 to 6 years after lung cancer resection 178 (right panel Fig. 1). Thus, in the left panel, physical activity addresses the cause of the disease, while in the right panel, physical activity only acts as a treatment against a disease in which it cannot prevent. We will focus on the disease processes of the left panel in this article.

thumbnail image

Figure 1. Physical activity produces primary and tertiary preventive health benefits for chronic diseases. Left panel. Physical inactivity is an actual initiating cause of a chronic disease/condition. Restoration of physical activity (primary prevention) removes the actual cause (physical inactivity) that produced the health deficiency. Right panel. Physical inactivity is not the cause of lung cancer. Smoking is an actual cause of lung cancer. Addition of aerobic exercise training compensates (tertiary prevention) for loss of lung function after surgical removal of a portion of lung by strengthening respiratory skeletal muscles for remaining lung 178. Exercise does not cure lung cancer.

7 Mechanisms of Physical Inactivity and Activity Differ

  1. Top of page
  2. Organization of Article
  3. Definitions
  4. Overview for Next Three Sections
  5. Summary of Daily Step Reductions from Antiquity
  6. History of Inactivity's Compromising Effects on Function and Health
  7. Cause Versus Treatment
  8. Mechanisms of Physical Inactivity and Activity Differ
  9. Gene-Exercise/Physical Inactivity Interactions
  10. Twin Studies: Modulation of Twin Phenotype by Physical Activity
  11. Variety of Training Types to Primarily Prevent Disease
  12. Diseasome of Physical Inactivity (35 Diseases/Conditions)
  13. Inactivity Accelerates Loss of Functional Capacities with Years of Life
  14. Prevention of Death by Primary Prevention of Physical Inactivity
  15. Metabolic Syndrome
  16. Presentation Strategy for Diseases Composing MS
  17. Obesity
  18. Inactivity Fosters Obese Comorbidities
  19. Insulin Sensitivity/Resistance
  20. Prediabetes
  21. Type 2 Diabetes
  22. Nonalcoholic Fatty Liver Disease
  23. Cardiovascular Diseases: All Types
  24. Presentation of Individual Cardiovascular Diseases
  25. Coronary Heart Disease
  26. Peripheral Arterial Disease
  27. Hypertension
  28. Stroke
  29. Congestive Heart Failure
  30. Known Mechanisms for CVD Risk Factors
  31. Deep Vein Thrombosis
  32. Cognitive Function
  33. Depression and Anxiety
  34. Bone (Osteoporosis)
  35. Osteoarthritis
  36. Balance
  37. Rheumatoid Arthritis
  38. Cancer
  39. Colon Cancer
  40. Breast Cancer
  41. Endometrial Cancer
  42. Activity Prevention of Female Reproductive Disorders
  43. Activity Prevention of Male Reproductive Disorders
  44. Pain
  45. Digestive Tract Diseases
  46. Chronic Respiratory Diseases
  47. Chronic Kidney Disease
  48. Clinical Significance of Physical Inactivity as One Cause of 35 Chronic Conditions
  49. Effectiveness of Drug Therapy for Simultaneous Primary Prevention of 35 Physical Inactivity Conditions
  50. Risk Factors Worsen Over 6 to 12 Months in RCTs
  51. Primary Prevention of Physical Inactivity: Childhood Developing Adult Disorders
  52. Public Policy
  53. Conclusion
  54. Acknowledgements
  55. References

Mechanisms of physical inactivity are considered antiparallel, rather than in series (continuum) to physical activity 209, 569. Physical activity and inactivity reside in different mechanistic planes, and are not merely mirror images of each other as is commonly considered (discussed later). Optimal therapies and preventive strategies require knowledge of causal mechanisms. Thus, it is important to understand that some of the mechanisms by which inactivity causes chronic diseases differ from mechanisms by which exercise acts as primary prevention of same diseases.

One example is that inactivity and exercise differ with regards to time courses of structural changes in conduit arteries and changes in endothelial function. This difference is summarized nicely in a review where Thijssen et al. state: “However, the nature and impact of inactivity and exercise on vascular structure and function suggest that inactivity and exercise are not simply the opposite ends of a linear spectrum of physiological adaptation” 505. In our Figure 2, distinct mechanisms by which inactivity and/or exercise alter conduit size and endothelial function are outlined. For instance inactivity results in immediate negative remodeling of the vessel, while activity requires 4 to 6 weeks to positively remodel the vessel.

thumbnail image

Figure 2. Changes in artery function and structure (remodeling) show differential time courses in response to increasing or decreasing human physical activity as hypothesized by Thijssen et al. 505. Exercise training (right side) produces early, rapid increases of arterial function (blue line), which is followed weeks later by arterial remodeling (red line and larger diameter vessel) that returns arterial function to pre-exercise training levels. Physical inactivity (left side) is associated with immediate, rapid decreases in arterial diameter after spinal cord injury (decreased size in top far left blood vessels and red line). Function immediately decreases and then returns to preinjury value.

Reproduced, with permission, from Figure 2 in reference 505.

A second example that inactivity and exercise are not mirror images of one another is found from global analysis of skeletal muscle gene expression, before bed rest, immediately after bed rest, and after 4 weeks of post-bed rest training. Compared to pre-bed rest levels, 9 days of bed rest altered 4500 mRNAs. If physical activity were merely the reverse of inactivity then all 4500 would be hypothesized to return to pre-bed rest levels following 4 weeks of training. However, a normalization of expression failed to occur in 20% of the 4500 genes that changed with bed rest. This observation led Alibegovic and co-workers 8 to speculate that rather severe and long lasting adverse alterations in mRNA levels may develop in important biological pathways relevant to their general health after 9 days of bed rest.

A third example is by Stein and Bolster 490 who compared muscle atrophy 310 to skeletal muscle regrowth from atrophy 183, and reiterated by Greenhaff and Hargreaves 209. Again, if physical activity were the opposite of physical inactivity, then the expected result would be many of the same genes changes would be similar for atrophy and regrowth. However, comparison of these two gene lists showed virtually no common gene names on both lists. These examples illustrate a fundamental principle of biochemistry, which Stein and Bolster concisely state, “This is a common finding in biochemistry. Anabolic and catabolic pathways are usually separate” 490, or put another way, opposite processes work through entirely different mechanisms rather than altering the level of one pathway. Further biochemical examples include; irreversible steps in glycolysis and glycogen synthesis, protein synthesis and degradation, lipolysis and lipogenesis, and mitochondrial biogenesis and mitophagy, all of which support the idea that exercise and inactivity are not merely opposites of each other. Thus, a single molecular paradigm to explain adaptations to exercise and inactivity does not exist.

8 Gene-Exercise/Physical Inactivity Interactions

  1. Top of page
  2. Organization of Article
  3. Definitions
  4. Overview for Next Three Sections
  5. Summary of Daily Step Reductions from Antiquity
  6. History of Inactivity's Compromising Effects on Function and Health
  7. Cause Versus Treatment
  8. Mechanisms of Physical Inactivity and Activity Differ
  9. Gene-Exercise/Physical Inactivity Interactions
  10. Twin Studies: Modulation of Twin Phenotype by Physical Activity
  11. Variety of Training Types to Primarily Prevent Disease
  12. Diseasome of Physical Inactivity (35 Diseases/Conditions)
  13. Inactivity Accelerates Loss of Functional Capacities with Years of Life
  14. Prevention of Death by Primary Prevention of Physical Inactivity
  15. Metabolic Syndrome
  16. Presentation Strategy for Diseases Composing MS
  17. Obesity
  18. Inactivity Fosters Obese Comorbidities
  19. Insulin Sensitivity/Resistance
  20. Prediabetes
  21. Type 2 Diabetes
  22. Nonalcoholic Fatty Liver Disease
  23. Cardiovascular Diseases: All Types
  24. Presentation of Individual Cardiovascular Diseases
  25. Coronary Heart Disease
  26. Peripheral Arterial Disease
  27. Hypertension
  28. Stroke
  29. Congestive Heart Failure
  30. Known Mechanisms for CVD Risk Factors
  31. Deep Vein Thrombosis
  32. Cognitive Function
  33. Depression and Anxiety
  34. Bone (Osteoporosis)
  35. Osteoarthritis
  36. Balance
  37. Rheumatoid Arthritis
  38. Cancer
  39. Colon Cancer
  40. Breast Cancer
  41. Endometrial Cancer
  42. Activity Prevention of Female Reproductive Disorders
  43. Activity Prevention of Male Reproductive Disorders
  44. Pain
  45. Digestive Tract Diseases
  46. Chronic Respiratory Diseases
  47. Chronic Kidney Disease
  48. Clinical Significance of Physical Inactivity as One Cause of 35 Chronic Conditions
  49. Effectiveness of Drug Therapy for Simultaneous Primary Prevention of 35 Physical Inactivity Conditions
  50. Risk Factors Worsen Over 6 to 12 Months in RCTs
  51. Primary Prevention of Physical Inactivity: Childhood Developing Adult Disorders
  52. Public Policy
  53. Conclusion
  54. Acknowledgements
  55. References

Physical fitness and physical activity/inactivity interact with genes. While many fitness examples of gene environment could be chosen, Vo2max will be used because it is well studied and integrates the function of multiple organs at multiple levels (i.e., tissue, cell, protein, and gene).

8.1 Genetic component alone

8.1.1 Phenotype responsiveness variability to aerobic training

Using untrained pairs of monozygotic (MZ) twins, dizygotic twins, and brothers approximately 40% to 50% of Vo2max was estimated to be due to genetics 57. Similarly, pairs of identical twins had significantly more similar increases in Vo2max than unrelated twin pairs after aerobic training in three papers in the mid-1980s 216, 420, 473. The papers led to the milestone paper reporting that some individuals experiencing little or no gain in Vo2max, whereas others gained more than1.0 liter/min in 481 sedentary subjects 55. A 2.5-times greater variance existed between families than within families in the Vo2max response variance.

8.2 Higher Vo2max associates with better health

The 1996 US Surgeon General's Report 530 concluded that high CRF decreases the risk of CVD mortality. High Vo2max is associated with “positive health”; low Vo2max is associated with “negative health.” Remarkably, low CRF was a stronger predictor of death than clinical variables or established risk factors, such as hypertension, smoking, and diabetes, as well as other exercise-test variables, including ST-segment depression, the peak heart rate, or the development of arrhythmias during exercise in both healthy subjects and those with CVD 362. Specifically, subjects aged 60 and older with low CRF had notably higher mortality risk from all causes than those with high CRF 498. Maintaining the highest possible Vo2max is a primary preventer of morbidity and mortality from low Vo2max (discussed later). Further information on the role of genes, physical activity, Vo2max (CRF), and health is presented next.

8.3 Using Vo2max to identify “health” genes

8.3.1 Theoretic selection of specific genes to optimize functional capacities

In 1979, Bennett and Ruben elegantly described a basis for natural selection of genes by physical activity to maximize inherited potential Vo2max:

“We believe that this increased stamina and sustainable activity were important selective factors from the outset…. The selective advantages of increased activity capacity are not subtle but rather are central to survival and reproduction. An animal with greater stamina has an advantage that is readily comprehensible in selective terms. It can sustain greater levels of pursuit or flight in gathering food or avoiding becoming food. It will be superior in territorial defense or invasion. It will be more successful in courtship and mating 34.”

The quotation hints that some genes were selected during evolution to support high levels of physical activity and the ability to adapt to physical activity. However, recent observations that a small portion of the population is low responder for Vo2max suggest a greater biological complexity than known in 1979.

8.3.2 Genes associated with plasticity of Vo2max

In 1998, Bouchard and coinvestigators published, “Maximal heritability estimates were at least 50%, a value inflated to an undetermined degree by inclusion of nongenetic shared factors” 56. Timmons employed a novel approach to improve the examination of complex physiological variables in human models. To identify genes responsible for variance of Vo2max plasticity, Timmons et al. 516 used a novel approach by first conducting mRNA expression microarray profiling, which were then used to produce molecular predictors to locate or rank a discrete number of genes that correlate with the change in Vo2max following endurance training. Follow-up studies allowed for subsequent targeted genotyping and, hence, discovery of key genetic variants responsible for the variance of Vo2max plasticity. A signature of 29 mRNAs and of 11 single nucleotide polymorphisms (SNPs) were identified that predicted approximately 50% and 23%, respectively, of the estimated variance for Vo2max plasticity following aerobic training in humans 516. Timmons et al. 516 noted two remarkable characteristics in their identified 29 predictor mRNAs: (i) pretraining levels were greater in high than low responders for Vo2max and (2) more than 90% of the 29 mRNAs did not change with aerobic training. They suggested that individuals with a low responder predictor gene profile would require alternative exercise intervention paradigms or more intensive pharmacological and dietary protocols to help compensate for their genomic profile. Timmons and coauthors further examined the same subjects after 6 weeks of endurance training at 70% of maximal Vo2max 516. They observed that low responders did not switch on their proangiogenic network genes effectively 268.

Timmons et al.'s 516 development and validation of mRNA predictors to hunt for genetic markers have many advantages over existing approaches of SNP. Each SNP seems to contribute only weakly for chronic complex human diseases. For example, after genome-wide association analysis in T2D patients, 18 robust SNPs explain less than 7% of the total disease variance 483. As to generalization of a low responder to all of tens of health benefits from exercise training from Vo2max alone, Timmons cautions, “No systematic analysis allows us to be certain that a “nonresponder” for one trait does not cluster with a poor response for another” 515. Thus, additional research is needed to determine whether low responders for gain in Vo2max with endurance training respond to other “positive health” benefits of physical activity, such as improved cognitive function, bone density, skeletal muscle strength, VAT quantity and quality, and the tens of other “positive health” benefits detailed later in this article 53. Sisson and co-workers 477 reported that nonresponders to for increase in Vo2max comprised a total of 44.9%, 23.8%, and 19.3% of the 4-, the 8-, and the 12-kcal/kg/week treatment groups, respectively. They concluded that greater volumes of exercise were associated with a lower probability of being a nonresponder. In summary then, additional research is needed to determine if low responders to aerobic exercise are low or high responders to high-intensity interval training (HIT), to resistance training (RT), balance, or flexibility training.

8.3.3 Proof due to experimental selection of physical aerobic-fitness genes in animals

Britton and Koch's experimental selection, based upon a single volitional/behavioral forced running test to exhaustion, provided experimental evidence that natural selection for high aerobic capacity during evolution is a feasible concept 568. Selection of rats on the basis of the longest or shortest running distances during a single exercise test resulted in selection of a 58% higher aerobic capacity in the high-distance line than the short-distance line over 11 generations. Rats with high Vo2max had healthier cardiovascular systems (12% lower mean 24-h blood pressures and 48% better acetylcholine-induced vasorelaxation), and healthier metabolic risk factors (16% less fasting plasma glucose, 39% less VAT, 63% lower plasma triglyceride levels, and greater mitochondrial protein concentrations). These data provide evidence of a genetic role in interanimal variation in Vo2max that is correlated with better health outcomes.

8.4 Phenotype responsiveness variability to resistance training

In addition to Vo2max variance among subjects in response to aerobic training, RT also has a tremendous amount of variability in adaptive responsiveness. In 585 subjects undergoing 12 weeks of RT, changes from 2% to +59%, 0% to +250%, and −32% to +149% occurred in cross-sectional area, one repetition max, and maximal isometric contraction, respectively 249. The variability in muscle mass may, in part, be related (but not limited) to interindividual differences in genome code (as with IGF2 in the aforementioned porcine model) 376, the individual's ability to activate intramuscular mTORC1 signaling within skeletal muscle in response to exercise 332, and/or different responses of microRNA (miRNA) to RT 120. Successful RT-induced hypertrophy in human skeletal muscle was associated with specific differences in miRNA expression to RT in high and low responders, respectively, which Davidsen et al. 120 suggest means that miRNAs may play a role in regulating the translation of key gene networks responsible for human skeletal muscle growth. One possible pathway is the PI3K/Akt/mTOR pathway, which is upregulated during skeletal muscle hypertrophy in humans, and related to the ability for satellite cells to proliferate and/or differentiate 410.

8.5 Pharmacogenetics interactions with exercise

The efficacy of drugs is affected by physical fitness/activity status 104, 327 in addition to genetic disposition. For instance, in patients with abnormal LV relaxation and preserved LV ejection fraction, exercise and weight loss plus drug reduced the LV relaxation dysfunction that was not reduced by the drug alone 104. Martin et al. 327 speculate that drugs with good efficacy in sedentary overfed (overweight) animal models may be less effective in active normal weight animals.

8.6 The future of personalized human medicine

The findings of the previous sections have led Timmons et al. 516 to predict that they could apply gene data for changes in Vo2max in personalized medicine to tailor exercise prescription. Medicine will continue to become more personalized with the looming question of how to optimize how it is applied to ensure the greatest patient benefit. Carl Sagan wrote, “It is the tension between creativity and skepticism that has produced the stunning and unexpected findings of science” 451. It is the spirit of Sagan's quotation that we now raise issues about which we are skeptical. We are skeptical that exercise experts will be used to inform health care professionals on how to make personalized exercise prescriptions based on science. The fear is that a patient will be informed that they have low-responder genes for Vo2max, which may lead to failure of the patient to exercise or lack of compliance to alternative exercise prescriptions. We hope that solutions, such as encouraging low responders to aerobic exercise or to engage in resistance exercise, can lead to striking improvements in personalized health.

8.7 Clinical significance

In a statement in Science, NIH Director Francis Collins wrote:

However, the best opportunity to reduce risk in genetically susceptible people for the foreseeable future will not be to reengineer their genes, but to modify their environment. We need to understand how genetic factors and environmental exposures interact in individuals to alter normal biological function and to affect the risk of disease development 463.”

The clinical significance of low and high responders for a given dosage and type of exercise, implies that individualized medicine, if exclusively restricted to viewing genetic background in vacuum, will result in less than optimal prescriptive therapy. Rather, individualized medicine for primary prevention of disease and premature death must also be based on individualized variation of inherited genes for: (i) disease susceptibility, (ii) responsiveness to exercise training and type of exercise, and (iii) drug-exercise interactions, if appropriate. Thus, fully capturing personalized gene-environment interactions.

Kujala et al. 288 wrote:

“When tailoring clinical physical activity interventions, we must remember that not all individuals are suited to the same guidelines for exercise intensity, because the ability to exercise seems to vary not only by training background but also by genetic predisposition.”

9 Twin Studies: Modulation of Twin Phenotype by Physical Activity

  1. Top of page
  2. Organization of Article
  3. Definitions
  4. Overview for Next Three Sections
  5. Summary of Daily Step Reductions from Antiquity
  6. History of Inactivity's Compromising Effects on Function and Health
  7. Cause Versus Treatment
  8. Mechanisms of Physical Inactivity and Activity Differ
  9. Gene-Exercise/Physical Inactivity Interactions
  10. Twin Studies: Modulation of Twin Phenotype by Physical Activity
  11. Variety of Training Types to Primarily Prevent Disease
  12. Diseasome of Physical Inactivity (35 Diseases/Conditions)
  13. Inactivity Accelerates Loss of Functional Capacities with Years of Life
  14. Prevention of Death by Primary Prevention of Physical Inactivity
  15. Metabolic Syndrome
  16. Presentation Strategy for Diseases Composing MS
  17. Obesity
  18. Inactivity Fosters Obese Comorbidities
  19. Insulin Sensitivity/Resistance
  20. Prediabetes
  21. Type 2 Diabetes
  22. Nonalcoholic Fatty Liver Disease
  23. Cardiovascular Diseases: All Types
  24. Presentation of Individual Cardiovascular Diseases
  25. Coronary Heart Disease
  26. Peripheral Arterial Disease
  27. Hypertension
  28. Stroke
  29. Congestive Heart Failure
  30. Known Mechanisms for CVD Risk Factors
  31. Deep Vein Thrombosis
  32. Cognitive Function
  33. Depression and Anxiety
  34. Bone (Osteoporosis)
  35. Osteoarthritis
  36. Balance
  37. Rheumatoid Arthritis
  38. Cancer
  39. Colon Cancer
  40. Breast Cancer
  41. Endometrial Cancer
  42. Activity Prevention of Female Reproductive Disorders
  43. Activity Prevention of Male Reproductive Disorders
  44. Pain
  45. Digestive Tract Diseases
  46. Chronic Respiratory Diseases
  47. Chronic Kidney Disease
  48. Clinical Significance of Physical Inactivity as One Cause of 35 Chronic Conditions
  49. Effectiveness of Drug Therapy for Simultaneous Primary Prevention of 35 Physical Inactivity Conditions
  50. Risk Factors Worsen Over 6 to 12 Months in RCTs
  51. Primary Prevention of Physical Inactivity: Childhood Developing Adult Disorders
  52. Public Policy
  53. Conclusion
  54. Acknowledgements
  55. References

Claude Bouchard has extensively used the experimental approach of MZ twins to minimize genetic variability for estimating the percentage contribution of environmental (physical activity) interventions since the mid-1980s. In addition to studies where twins were subjected to exquisitely controlled exercise protocols, a number of studies used overfeeding protocols to look at the effect of excess calories (not included in the following tables). The twin approaches have been critical to our ability to separate genetic from environmental effects related to health and chronic disease in humans. Future twin-activity studies will contribute to prescription of exercise types and of dose-response thresholds for primary prevention of chronic diseases.

9.1 Comprehensive presentation of twin-activity (gene-environment) studies

In this section, we take the approach of searching the literature for all articles (that we could find) that have examined a variety of health outcomes in MZ twins to attempt to control for genetic variation.

9.2 MZ twin-activity comparisons show high-mortality component

To summarize the most important health outcome, mortality, Table 2 is presented to show the mortality outcome in MZ twins discordant for physical activity in a large cohort of Swedish twins 77. The higher physically active MZ had a 36% to 66% lower mortality than their inactive MZ pair.

Table 2. Tendency for Dose-Response Between Higher Physical Activity Level and Lower mortality in Swedish Monozygotic Twins [Modified from 77]
  All-cause mortalityCardiovascular mortality
SexPhysical activity levelHazard ratio95% confidence intervalsHazard ratio95% confidence intervals
  1. Questionnaire used with seven items: low physical activity (“almost never” and “hardly ever”) level; moderate (“very little,” “not much,” and “quite much”); and high (“a lot” and “very much”).

MenLow1 1 
 Moderate0.840.72, 0.980.860.68, 1.08
 High0.640.50, 0.830.550.36, 0.85
WomenLow1 1 
 Moderate0.820.70, 0.960.850.64, 1.13
 High0.750.50, 1.140.340.1, 0.95

9.3 MZ twin-activity comparisons show variable chronic disease component

These studies have taken the approach of either a priori separating pairs of MZ that are discordant for physical activity (Table 3), looking at exercise responses in MZ twins relative to dizygotic twins (Table 4), correlating health parameters with physical activity or fitness levels in MZ twins (Table 5), and looking at the genetic component of physical fitness and activity parameters (Table 6). By evaluating this approach, we can obtain an idea about which factors are controlled mainly by genetics and which are most modifiable for physical activity levels. However, it should be noted that many of these studies have methodological limitations including a wide range of physical activity levels and outcomes that differ from classical exercise physiology adaptations.

Table 3. Studies with Twin Discordant for Physical Activity Levels
OutcomesPhysical inactivity effectMZ, nOther, nSexPA measurementCommentsReferences
  1. Studies with Twin Discordant for Physical Activity Levels

  2. Abbreviations: B, both sexes; DZ, dizygotic; E, exercise component; G, genomic component; M, men; MZ, monozygotic; N.S., nonsignificant; PA, physically active; W, women; [UPWARDS ARROW], increase; [DOWNWARDS ARROW], decrease

MRI visceral fat

MRI liver fat score

MRI intramuscular fat

[UPWARDS ARROW] 50% in inactive twin

[UPWARDS ARROW] 170% in inactive twin

[UPWARDS ARROW] 54% in inactive twin

16 BQuestionnaireAge of 50-74 years and followed for over 32 years. Subset for Finnish twin study.315

BW changes from 1975 to 2005

WC changes from 1975 to 2005

[UPWARDS ARROW] 5.4 kg for the inactive twin

[UPWARDS ARROW] 8.4 cm in inactive twin

 42 twins MZ to DZ proportions unclearBPhone interviewUnclear about proportion of MZ vs. DZ, but states no differences between MZ and DZ. Subset of Finnish twin study. Twins not discordant for PA had no difference in BW.544
BMI[UPWARDS ARROW] 0.33 BMI in nonvigorously active twin614 MSelf-reported vigorous activityAll males (mean age 41.1 years) that fought in Vietnam war. When looking at all twins modeling predicted no genetic effect on the relationship between vigorous activity and BMI.334

Weight gain

Waist circumference

[UPWARDS ARROW] 5.4 kg inactive twin

[UPWARDS ARROW] 8.4 cm in inactive twin

42 BQuestionnaire showing discordant PA in 1975, 1981, and 2005Finnish twin study.544
Total body fat in women with similar weight[UPWARDS ARROW] 1.0 and 1.4 kg fat for 1-h or 2-h less activity per week156WQuestionnaire home, sport, sweating activitiesDiscordant for physical activity. Age of 55.5 years.454
Total and regional body fat in women with discordant weight[UPWARDS ARROW] 3.96 kg lower BF and 0.53 kg centralAlso showed increased physical activity increased muscle mass and strength (not analyzed in discordant twins). 

BMI

HDL

HDL2

Apo A-1

[UPWARDS ARROW] 2.12 in inactive twin (P < 0.001)

[DOWNWARDS ARROW]0.14 in inactive (P = 0.004)

[UPWARDS ARROW] 2.71 in inactive (P = 0.001)

[UPWARDS ARROW] 0.10 in inactive (P = 0.004)

35

 Healthy Runners Survey − high PA = 40 km/week > than low PA (male), 32 km/week (female)Subjects recruited from the National Healthy Runners Survey. No active twins with overweight twin were themselves overweight.562
Lipid profile before and after 40% fat or 20% fat diet (crossover study): LDL and subfractions, apolipoprotein A-1N.S.28 MSurvey. One twin running > 50 km/week than other twinSubjects recruited from the National Healthy Runners Study. A diet low in fat independent of high amounts of exercise modifies circulating lipids.563
Adiposity[UPWARDS ARROW] Sig lower in inactive twin21 F9 months of 3 d/wk high-intensity weight bearing activityGirls were prepubertal aged 8.7. Did not tell the control group that they could no longer participate in sports.533

BMD

aBMC

N.S.

[DOWNWARDS ARROW] Sig in inactive twin

12  Lifetime leisure high-impact sportsSubgroup from the original group.533
Femoral neck and lumbar BMDE = 1% and G = 73% of lumbar variance105 MQuestionnaire for endurance and balls sportsFinnish men (35-69 years old) Calcium supplements also explained 1% of difference in BMD.540
Spinal MRIN.S. disk degeneration22 MQuestionnaire between 1975 and 1981 showing discordant endurance PA (3.9 vs. 1.1 time/week)Finnish twin cohort aged 35-69 years.541
 [DOWNWARDS ARROW]T6 disk degeneration in low strength PA twin12 MQuestionnaire between 1975 and 1981 showing discordant strength PA (2300 vs. 200 h)Finnish twin cohort aged 35-69 years.541
Psychomotor reaction times[DOWNWARDS ARROW] Sig slower choice reaction for hand and contra foot in inactive38  Lifetime exercise historiesFinnish twin cohort. Average age of discordant PA twins is 50. PA data collected in 1972, 1981, and 1992.474
Psychological functioning (mood, optimism, and control)[DOWNWARDS ARROW] Sig in inactive twin63 BQuestionnaire for discordant vigorous activityFrom US National Survey of Midlife Development.257
Survey-based anxiety and depression symptomsN.S.??BLeisure time PA onlyArticle is unclear how many MZ twins were discordant for PA in their models. Only current levels of PA and not PA history used. Used Dutch population, but excluded cycling to work as PA (nonleisure).126
Dementia[UPWARDS ARROW] P = 0.07 for inactive PA twin90 BTwin registry reported 31 years before follow-upSwedish twin registry. Data on all twins showed significant correlation of increased PA and decreased dementia.12

Life satisfaction

Life happiness

N.S.

N.S.

16

1

1722842SurveyData in MZ and related family members showed an OR > 1.0 for active pair of an unrelated paired of people.497

Lactate threshold

Vo2max

Total body fat

E is 25%-30% and G is 50%-60%

E is 35% and G is 45%

E is 20% and G is 70%

9 M6 months of anaerobic threshold trainingAged 11-14 years. Change in Vo2max was more due to the less weight gain in trained twin. Used analysis of variance to estimate the genetic and training effects.119
Myocardial infusion at rest, during adenosine, and cold-pressor testN.S.9 MSeparated by Vo2max and physical activity levelsYoung males with a 18% difference in Vo2max (mL/kg/min) of (43.7 vs. 50.7).220

Endothelial function via ultrasound of brachial and LAD coronary artery

Oxygen extraction fraction

N.S.

[UPWARDS ARROW] in low fit (P = 0.06)

     220

Hepatic FFA uptake at rest

Myocardial FFA uptake at rest and during exercise

[UPWARDS ARROW] Sig in less fit group

N.S.

    Same subjects as reference 220.221
Skeletal muscle perfusion and free fatty acid uptakeN.S.    Same subjects as reference 220.222

Cornell voltage (electrical measurement of LV hypertrophy)

Right-side hypertrophy index

LV mass index

[DOWNWARDS ARROW] Sig in inactive     36
Type 2 diabetes18 inactive vs. 2 active twins acquired T2DM515 DZBLeisure time PATwins discordant for PA and discordant for type 2 diabetes. For MZs, it was the inactive twin that developed type 2 diabetes.287
Mortality from 1975 to 1981[UPWARDS ARROW] Sig in inactive DZ twins, but not inactive MZ twins157517BQuestionnaires for vigorous PA and estimates of > 2 MET week/day/weekFinnish twin cohort aged 24-60 years. Low level of leisure physical activity in early life was associated with increased risks of death in dizygotic twin pairs, but monozygotic cotwins.

Table 4. Studies with Twin Response to Exercise
PA interventionOutcomesH effectMZ, nDZ, nSexCommentsReferences
  1. Studies with Twin Response to Exercise

  2. Abbreviations: B, both; DZ, dizygotic; H, heredity effect; M, male; monozygotic; N.S., nonsignificant; n, number of subjects

Submaximal supine bicycle at HR of 110 bpm

End-diastolic mean wall thickness (rest)

LV diameter (rest)

Fractional shortening (rest)

Change in end-diastolic mean wall thickness w/exercise

Change LV diameter w/exercise

Change in Fractional shortening w/exercise

Cycling power output

Cycling Vo2max

H = 53%

N.S

H = 13% (N.S)

H = 0% (N.S.)

H = 24%

H = 47%

H = 53%

H = 46%

2112MSimilar results when adjusted for body fat. Nongenetic component is made up of both shared and nonshared environmental components.40
20-week endurance trainingLV wall, posterior wall, septal wall, and LV massMinimal H effect20

20 (not

related)

MTraining effect in all subjects.302
Supine bicycle at 60 W (submaximal)

SBP (rest)

DBP (rest)

Change in SBP w/exercise

Change in DBP w/exercise

Sig H3221MLess effect on heritability during exercise than at rest (conclusions based only on abstract; unable to obtain full article).41
Graded cycle test to “exhaustion”Peak Vo2H = 77%, 66% when PA and skinfolds adjusted2919MTesting was done on a max test and also collected with HR was at 150 bpm.175
O2 uptake at HR of 150 bpmH = 61%, 16% when PA and skinfolds adjusted     
Mechanical efficiencyN.S. H correlation     
Anaerobic energy generationH = 78%, 58% when PA and skinfolds adjusted     
Respiratory exchange ratioH = 6% only     
30 min of treadmill at anaerobic thresholdGH and PRL response to exercise and cortisol at restSig H correlation9MAthletes135
ACTH and cortisol response to exercise and β-endorphin at restN.S. H correlation9 M  

93 days of negative energy balance (diet and exercise)

Euglycemic-hyperinsulinemic clamp before and after intervention

Fasting and postprandial insulin

N.S. H correlation

7M389
Dehydroepiandrosterone sulfate and androsterone glucuronideSig H effect7MHealthy young males.418
 Cortisol levels      
Wingate test and max progressive test

Max 5 s Wingate power

Max lactate wingate

Delta lactate during maximal test

H = 74%

H = 82%

H = 84%

88Not correlated were measures in the ergo jump test. Had different heritability's with different tests measuring same performance measure. Homogenous subject group.75
10-week isokinetic strength training (5 d/week)

HK, MDH, and B-HAD

Oxoglutarate dehydrogenase activity (OGDH)

N.S. H

Sig H

55 (unrelated)M504
Maximal and submaximal treadmill running

Running economy

Vo2max

Maximal lactate

N.S. H correlation

N.S. H correlation

H = 75%

88No significant differences in references to MZ vs. DZ twins.439
15 weeks of endurance trainingSkeletal muslce HKII, (31%), PFK (37%), LDH (21%), MDH (31%), and B-HAD (60%)Sig H12M216
Fiber-type and CK activitiyN.S. H     
15 weeks of high-intensity supramaximal exercise (4-5 times/week)

ALC, CK, HK, LDH, MDH, OGDH activitiy, and PFK:OGDH activity ratio

Fiber type and anaerobic capacity

Sig H28Exercise bouts of 15-90 s all out.473
A single 90-min bout of exerciseRest vs. ex-adipose LPL activity following exerciseSig difference between MZ and DZ1110MAged 18-27 years.457
Cycle exerciseRest vs. ex-metabolic rate (Vo2)H = 46% at low power. N.S. H at >6xRMR3721 + 31 parent childB 60
Cycle exercise to maxAbsolute and BW adjust Vo2maxSig H1212M18-31 years old.176
Rest vs. ex-LV internal diameterN.S. H     
Rest vs. ex-fractional shorteningN.S. H     
LV massN.S. H when adjusted for BW     
165 min submax treadmill test before and after 22 days of 1000 kcal/d overfeedingPre vs. postchange in Vo2maxSig H12 M 523
93 days of supervised 60 min/d exerciseLoss in BW, fat mass, skinfold, and visceral fatSig H7MHealthy young males.59
Change in fasting TAGs and cholesterol      
Change in Vo2max and RER during exercise      
1000 kcal of vigorous exercise per day for 22 days

Pre vs. postfasting insulin

Pre vs. post delta insulin during OGTT

Sig H

N.S. H

12MHealthy young males.521
93 days of supervised 60 min/d exercisePre vs. postfasting insulin and glucose disposalN.S. H, but Sig improvement7   389
116 min/d of cycle ergometer for 22 days at 58% max

Pre vs. postfat mass

Basal lipogenesis

Pre vs. postinsulin stimulated lipogenesis

Pre vs. postepinephrine and basal lipolysis

Pre- vs. post-LPL activity

Fat-free mass

N.S. H

Sig H

N.S. H

N.S. H

N.S. H

Sig H

12MHealthy males aged 19.1 years old.413
20-week cycle ergometer endurance training

Pre vs. postepinephrine lipolysis

Basal lipolysis

Sig H

N.S. H

8BFour males and four females.133
Single 90-min bout of exerciseLPL activityMore Sig in MZ than DZ1110M 457
116 min/d of cycle ergometer for 22 days at 58% max

Total cholesterol

LDL cholesterol

HDL cholesterol

Sig H12M134
93 days of supervised 60 min/d exercise

Total cholesterol

LDL cholesterol

Cholesterol to HDL ratio

Sig H7MMale, young, and healthy. Approximately 93,000 total calorie deficit. Significant within twin effects.297
116 min/d of cycle ergometer for 22 days at 58% max

Baseline RMR

Baseline thermic effect of food

Pre vs. postplasma T3, T4, and FT4

Sig H

Sig H

Sig H (except for T3)

12M414
93 days of supervised 60 min/d exercise

Pre vs. post-RMR, thermic effect of food

Thyroid hormones

Sig H7MHealthy young males.522
14 weeks of exercise trainingCardiac sizeN.S. H2810 + 12 siblingsBNo genetic effect on heart size pre- or postexercise training.3
Table 5. Studies with Twin Correlations That Are Corrected for PA Levels or Unique Environmental Effects (Twins May Not Be Discordant for PA)
OutcomesH effectPA effectMZ, nDZ, nSexPA measurementCommentsReferences
  1. Studies with Twin Correlations That Are Corrected for PA Levels or Unique Environmental Effects (Twins May Not Be Discordant for PA)

  2. Abbreviations: B, both; DZ, dizygotic; F, female; H, heredity effect; M, male; monozygotic; N.S., nonsignificant; n, number of subjects; [UPWARDS ARROW], increase; [DOWNWARDS ARROW], decrease

Weight gain[DOWNWARDS ARROW] correlation in inactive 15713029BQuestionnaire of physical activity levels at baselineFinnish twin study. At all activity levels MZ twins had greater hereditability than DZ twins.230

Waist circumference

BMI

[UPWARDS ARROW] 2.5 cm in low PA twin

N.S.

287189Questionnaire in 1998 and 2002. Only looking at leisure and occupational PANo analysis for discordant PA. If twins had large genetic susceptibility then low PA resulted in larger increase in WC.265

Waist circumference

Waist-hip ratio

BMI

76% (M); 77% (F)

59% (M); 56% (F)

89% (M); 73% (F)

21% (M); 22% (F)

36% (M); 38% (F)

11% (M); 27% (F)

7175BQuestionnaireAfrican Americans aged 22-88 years from Carolina African American Twin Study of Aging. All effects are unique environemental not just PA levels.373
Discordant for BMI by at least 3 N.S.23 BInterviews and questionnaire for PANo significant effects of PA on the discordance of overweight prevalence.213
Discordant for obesity [DOWNWARDS ARROW] fitness (8%) and activity (15%) in obese twin14 MVo2max and Baecke leisure time PAFrom Finnish Twin Study—obese also had lower adipose mitochondrial gene expression.361
Subscapular: triceps body fat ratio24%265M“Crude” measure of PAPA was inversely related to adjusted waist circumfrance.467
Waist circumference46%       

Diastolic BP

Aerobic exercise amount

35%

44%

5%

N.S.

71104BInterview: lifetime exercise divided into power, aerobic, or otherAerobic exercise in adolescence lifetime high-intensity aerobic associated with low diastolic BP throughout life (mean age of 50 at study time).235
“Augmentation index” or systemic arterial stiffness [UPWARDS ARROW] Sig in high genetic risk group when inactive53262 + 54 singletonsFQuestionnaires 208
MZ subjects that are discordant for hypertension Hypertensive twin [UPWARDS ARROW] being inactive (after military service)281 MSurvey from the National Heart, Lung, and Blood Institute (NIH)Twins whom are veterans of World War II aged 55-66 years. Surveyed at time of entry to military and time of study.78
HDL cholesterolCorrecting for genetics prevent correlation[UPWARDS ARROW] correlation between exercise and HDL179255FQuestionnaire (one question about PA)Kaiser Twin Registry in Oakland, CA. aged 18-85 years.105

Lumbar spine disk degeneration

Lumbar spine disk degeneration

74%

73%

N.S.

N.S.

172154BInterviewed about weight bearing exerciseNo effect of adjustment for exercise on lumbar or cervical disk degeneration.455
Total body BMC (DEXA)1.2% less in inactive twin/h of less exercise3026Questionnaire for weight-bearing exerciseAssociated was not present in prepubescent twins.253
Leg BMC[DOWNWARDS ARROW] 1.4% in inactive      
Spine BMC[DOWNWARDS ARROW] Sig in inactive      
BMD N.S.12293F12-month recall questionnaire for sport activity10-26 years old from Australian Twin Registry.576
Smoking likelihood at follow-up (about 4 years) [UPWARDS ARROW] 3.36× for inactive twin to be regular smokers97339BSurvey for twins discordant for PA (three categories used) at baselineAdolescents from a Finnish Twin Registry. Did not analyze by zygosity.289
Discordant prevalence of non-Alzheimer dementias [UPWARDS ARROW] risk correlated with physical inactivity106  Questionnaire administered 30 years beforeSwedish Twin Registry average age of first questionnaire was 48 years.194
Twins discordant for chronic fatigue syndrome— cognitive functioning tests pre-postmax testCognitive tests did were N.S.No relationship to chronic PA was made21 

B

(19 M, 2 F)

Acute cycle ergometer to maxExercise caused no change in cognitive functioning acutely.103
Various cognitive functions> 15%< 80%14321715 + 268,496 siblingsMCycle W max/kgPA effect for all nonshared environmental effects.1
Table 6. Genetic Influence on Physical Activity, Exercise Levels, and Exercise Capacity
PA measurementH effectUnique environmental effect (unless noted)MZ, nDZ, nSexCommentsReferences
  1. Genetic Influence on Physical Activity, Exercise Levels, and Exercise Capacity

  2. Abbreviations: B, both; DZ, dizygotic; F, female; H, heredity effect; M, male; monozygotic; N.D., not determined; n, number of subjects; Y, young

Isometric knee extensor strength56%42%206228

F

PA effect is nonshared environmental effects. All older women subjects (63-76 years old). New nonshared environmental effects responsible for differences at follow-up.514
Leg extensor power67%33%     
Isometric knee extensor strength (at 3-years follow-up)58%15%149164   
Leg extensor power (at 3-year follow-up)48%11%     
Elbow flexor muscle cross-sectional area43%6%2516MSubjects were young (22.4 years old) Caucasians from Belgium. Remaining variation accounted for by MCSA and environmental effects.125
Elbow flexor eccentric strength47%20%     
Elbow flexor isometric strength32%1%     
Leg extensor power32%4%101116FFinnish Twin Study on aging. Subjects 63-73 years old.513
Leg extensor strength48%52%     
Isokinetic lifting60%35%122131MFinnish Twin Study.445
Psychophysical lifting33%49%     
Isometric trunk extensor endurance5%61%     
Questionnaires based on country. > 60 min of 4 MET activity = exerciser26.5%-70.5%29.2%-51.9%13,67623,375BTwins from seven different countries. Australia had lowest genetic-highest unique environmental. UK females had highest genetic.496
Sports MET (> 4 MET activity in last 3 months)79% in Y, 41% Mid21% in Y, 57% Mid69 Y, 93 M88 Y, 105 MBYoung and middle age subjects.122
Questionnaire physical activity amount = 60-150 min/week

MZ = 45%

DZ = 30%

MZ = 55%1003386BTwins from the Washington State Twin Registry. The more PA you undergo the less the genetic influence there is.148
Questionnaire physical activity amount > 150 min/week (current guidelines)

MZ H = 31%

DZ= 25%

MZ = 69%     
Baecke and exercise questionnaire40%-65%60%-35%359232MNationwide Swedish twins. No shared environmental effect.165
Sport participation between ages of 13-16 years0%16%-22%10951533BDutch population. Does not include common environmental.495
Sport participation between ages of 17-18 years36%17%     
Sport participation after age of 18 years85%15%    495
Adulthood exercise43%26% from competitive sports121 MFinnish Twin Study. Also found that sports from ages 12-18 years was a predictor of adulthood exercise.475
Respiration chamber (doubly labeled H2O) activity-induced energy expenditure8%30%128BAged 17-39 years old. Univariate analysis using the additive genetic, but excluding the common environmental component.258
Respiration chamber physical activity by accelerometer0%59%     
Doubly labeled H2O-free living activity induced energy expenditure72%29%     
Free living PA by accelerometer78%22%     
RMR3%38%6238BAged 4-10 years. Correlations are corrected for body weight and do not include common environmental.188
Total EE by doubly labeled H2O19%23%     
Physical activity energy expenditure0%31%     
Vo2max, Vmax, and HRmax40%, 50%, and 60%N.D.10666BAlso 42 brothers included in the study.57
Fiber typeN.S.N.D.3526B32 brothers also included MZ twins had interpair correlation, but DZ and brothers suggested strong (but not quantified) environmental component.58
Skeletal muscle mitochondrial activitiesN.S.      
Oxidative to glycolytic ratio25%-50%      

As expected, many of the tested health parameters had both genetic and environmental components. In many studies, questionnaires were used to evaluate physical activity levels, a less than optimal method to collect such data. Thus, while the design of the studies analyzed was not optimized for elucidating the effects of physical activity independent of genotype, some cautious conclusions may be made from Tables 2-6, presented later.

9.4 Important physical activity component to activity adaptation

The data indicate that inactivity increases both visceral and total fat masses independent of genetic disposition. Additionally, Alzheimer's and dementia both have a large physical inactivity component. However, changes in muscle morphology (length, shortening velocity, of ventricular diameter) do not exhibit compelling genetic components. Genotype is apparently not a major determinant of the changes in insulin levels and sensitivity brought about by negative energy balance with exercise 389 (see Section “Insulin resistance” later in this article).

9.5 Important gene component to activity adaptation

In these studies, while physical activity levels themselves exhibit a large genetic component; it varies tremendously between countries and cultures. In addition to activity levels, a major genetic component is found for both measures of strength fitness (muscle strength and power) and in endurance fitness as well as responses (lactate levels and blood pressure) to exercise. More surprisingly is the minor effect of physical activity on overall “well-being,” which is in contrast to a number of cross-sectional studies suggesting that physical activity is strongly negatively correlated with depression and anxiety. Another surprisingly result is that twins discordant for physical activity do not differ in generalized bone mass or spinal cord bone mass 541, despite the well-known effects of bed rest and inactivity on increasing bone loss. These contradictory results may simply be due to the lack of specific measures of bone mass in the active limbs, or to the variation in types of load-bearing physical activities, and thus bone health, in the physically active group.

9.6 Clinical significance

Taken together, data in Tables 2-6 provide conclusive evidence that physical inactivity alone is sufficient to increase chronic diseases and death.

“Together, the 80 monozygotic publications unequivocally show that co-twins with lower physical activity levels exhibit increased risks for chronic diseases regardless of genotype. Such data, therefore, empowers physicians and other health care providers to prescribe physical activity as primary preventative medicine.”

10 Variety of Training Types to Primarily Prevent Disease

  1. Top of page
  2. Organization of Article
  3. Definitions
  4. Overview for Next Three Sections
  5. Summary of Daily Step Reductions from Antiquity
  6. History of Inactivity's Compromising Effects on Function and Health
  7. Cause Versus Treatment
  8. Mechanisms of Physical Inactivity and Activity Differ
  9. Gene-Exercise/Physical Inactivity Interactions
  10. Twin Studies: Modulation of Twin Phenotype by Physical Activity
  11. Variety of Training Types to Primarily Prevent Disease
  12. Diseasome of Physical Inactivity (35 Diseases/Conditions)
  13. Inactivity Accelerates Loss of Functional Capacities with Years of Life
  14. Prevention of Death by Primary Prevention of Physical Inactivity
  15. Metabolic Syndrome
  16. Presentation Strategy for Diseases Composing MS
  17. Obesity
  18. Inactivity Fosters Obese Comorbidities
  19. Insulin Sensitivity/Resistance
  20. Prediabetes
  21. Type 2 Diabetes
  22. Nonalcoholic Fatty Liver Disease
  23. Cardiovascular Diseases: All Types
  24. Presentation of Individual Cardiovascular Diseases
  25. Coronary Heart Disease
  26. Peripheral Arterial Disease
  27. Hypertension
  28. Stroke
  29. Congestive Heart Failure
  30. Known Mechanisms for CVD Risk Factors
  31. Deep Vein Thrombosis
  32. Cognitive Function
  33. Depression and Anxiety
  34. Bone (Osteoporosis)
  35. Osteoarthritis
  36. Balance
  37. Rheumatoid Arthritis
  38. Cancer
  39. Colon Cancer
  40. Breast Cancer
  41. Endometrial Cancer
  42. Activity Prevention of Female Reproductive Disorders
  43. Activity Prevention of Male Reproductive Disorders
  44. Pain
  45. Digestive Tract Diseases
  46. Chronic Respiratory Diseases
  47. Chronic Kidney Disease
  48. Clinical Significance of Physical Inactivity as One Cause of 35 Chronic Conditions
  49. Effectiveness of Drug Therapy for Simultaneous Primary Prevention of 35 Physical Inactivity Conditions
  50. Risk Factors Worsen Over 6 to 12 Months in RCTs
  51. Primary Prevention of Physical Inactivity: Childhood Developing Adult Disorders
  52. Public Policy
  53. Conclusion
  54. Acknowledgements
  55. References

Specificity of training [(i.e., adaptation to training is specific to the class of exercise (aerobic vs. resistance)] is dogma. For example, in 1976, one of us wrote that the nature of the exercise stimulus determines the type of adaptation 242. One type of adaptation involves hypertrophy of the muscle cells with an increase in strength; it is exemplified in its most extreme form by the muscles of weight lifters and body builders. The second type of adaptation involves an increase in the capacity of muscle for aerobic metabolism with an increase in endurance and is found in its most highly developed form in the muscles of competitive middle- and long-distance runners, long-distance cross-country skiers, bicyclists, and swimmers. Further, hypertrophied muscles of weight lifters did not have the increased mitochondria of aerobic training and that prolonged daily run training increases mitochondria, but does not hypertrophy the muscles. Application of the information to elderly individuals is that they must perform both types of exercise to prevent physical (endurance and strength) frailty.

Recent information expands and emphasizes the specificity dogma. HIT (near peak performance for short bursts alternating with longer periods of low-intensity aerobic activity) has been said to “prove more benefit than traditional continuous exercise programs in several metabolic, muscular, and cardiovascular parameters” 277. For example, HIT-walking resulted in greater increases in Vo2peak and thigh muscle strength and a greater reduction in systolic blood pressure (SBP) than moderate-intensity continuous walking in older men and women 374. In contrast, one HIT report indicates that HIT by untrained men produced greater (Vo2max), the same (improvements in oral glucose tolerance), and less [resting bradycardia, total-body fat percentage, and reducing ratio between total and high-density lipoprotein (HDL) plasma cholesterol] adaptations than in a second group performing continuous training 383.

11 Diseasome of Physical Inactivity (35 Diseases/Conditions)

  1. Top of page
  2. Organization of Article
  3. Definitions
  4. Overview for Next Three Sections
  5. Summary of Daily Step Reductions from Antiquity
  6. History of Inactivity's Compromising Effects on Function and Health
  7. Cause Versus Treatment
  8. Mechanisms of Physical Inactivity and Activity Differ
  9. Gene-Exercise/Physical Inactivity Interactions
  10. Twin Studies: Modulation of Twin Phenotype by Physical Activity
  11. Variety of Training Types to Primarily Prevent Disease
  12. Diseasome of Physical Inactivity (35 Diseases/Conditions)
  13. Inactivity Accelerates Loss of Functional Capacities with Years of Life
  14. Prevention of Death by Primary Prevention of Physical Inactivity
  15. Metabolic Syndrome
  16. Presentation Strategy for Diseases Composing MS
  17. Obesity
  18. Inactivity Fosters Obese Comorbidities
  19. Insulin Sensitivity/Resistance
  20. Prediabetes
  21. Type 2 Diabetes
  22. Nonalcoholic Fatty Liver Disease
  23. Cardiovascular Diseases: All Types
  24. Presentation of Individual Cardiovascular Diseases
  25. Coronary Heart Disease
  26. Peripheral Arterial Disease
  27. Hypertension
  28. Stroke
  29. Congestive Heart Failure
  30. Known Mechanisms for CVD Risk Factors
  31. Deep Vein Thrombosis
  32. Cognitive Function
  33. Depression and Anxiety
  34. Bone (Osteoporosis)
  35. Osteoarthritis
  36. Balance
  37. Rheumatoid Arthritis
  38. Cancer
  39. Colon Cancer
  40. Breast Cancer
  41. Endometrial Cancer
  42. Activity Prevention of Female Reproductive Disorders
  43. Activity Prevention of Male Reproductive Disorders
  44. Pain
  45. Digestive Tract Diseases
  46. Chronic Respiratory Diseases
  47. Chronic Kidney Disease
  48. Clinical Significance of Physical Inactivity as One Cause of 35 Chronic Conditions
  49. Effectiveness of Drug Therapy for Simultaneous Primary Prevention of 35 Physical Inactivity Conditions
  50. Risk Factors Worsen Over 6 to 12 Months in RCTs
  51. Primary Prevention of Physical Inactivity: Childhood Developing Adult Disorders
  52. Public Policy
  53. Conclusion
  54. Acknowledgements
  55. References

The term “diseasome of physical inactivity” was presented by Pedersen 402 to describe a clustering of diseases. Our article enlarges Pedersen's cluster to include over 35 diseases/conditions and death, which constitute most of the remaining article (Fig. 3). Joyner and Pedersen 259 contend that it is a failure of regulation at multiple levels that causes many common diseases. They further argue that a lack of fluency to use key physiological concepts (like homeostasis, regulated systems, and redundancy) as major intellectual tools to understand at multiple levels how whole animals adapt to exercise and maladapt to physical inactivity.

thumbnail image

Figure 3. Health deficiencies accelerated by decreasing physical activity from higher to lower levels. Gheorghe Constantinescu generously made original drawing.

Reproduced, with permission, from reference 52.

12 Inactivity Accelerates Loss of Functional Capacities with Years of Life

  1. Top of page
  2. Organization of Article
  3. Definitions
  4. Overview for Next Three Sections
  5. Summary of Daily Step Reductions from Antiquity
  6. History of Inactivity's Compromising Effects on Function and Health
  7. Cause Versus Treatment
  8. Mechanisms of Physical Inactivity and Activity Differ
  9. Gene-Exercise/Physical Inactivity Interactions
  10. Twin Studies: Modulation of Twin Phenotype by Physical Activity
  11. Variety of Training Types to Primarily Prevent Disease
  12. Diseasome of Physical Inactivity (35 Diseases/Conditions)
  13. Inactivity Accelerates Loss of Functional Capacities with Years of Life
  14. Prevention of Death by Primary Prevention of Physical Inactivity
  15. Metabolic Syndrome
  16. Presentation Strategy for Diseases Composing MS
  17. Obesity
  18. Inactivity Fosters Obese Comorbidities
  19. Insulin Sensitivity/Resistance
  20. Prediabetes
  21. Type 2 Diabetes
  22. Nonalcoholic Fatty Liver Disease
  23. Cardiovascular Diseases: All Types
  24. Presentation of Individual Cardiovascular Diseases
  25. Coronary Heart Disease
  26. Peripheral Arterial Disease
  27. Hypertension
  28. Stroke
  29. Congestive Heart Failure
  30. Known Mechanisms for CVD Risk Factors
  31. Deep Vein Thrombosis
  32. Cognitive Function
  33. Depression and Anxiety
  34. Bone (Osteoporosis)
  35. Osteoarthritis
  36. Balance
  37. Rheumatoid Arthritis
  38. Cancer
  39. Colon Cancer
  40. Breast Cancer
  41. Endometrial Cancer
  42. Activity Prevention of Female Reproductive Disorders
  43. Activity Prevention of Male Reproductive Disorders
  44. Pain
  45. Digestive Tract Diseases
  46. Chronic Respiratory Diseases
  47. Chronic Kidney Disease
  48. Clinical Significance of Physical Inactivity as One Cause of 35 Chronic Conditions
  49. Effectiveness of Drug Therapy for Simultaneous Primary Prevention of 35 Physical Inactivity Conditions
  50. Risk Factors Worsen Over 6 to 12 Months in RCTs
  51. Primary Prevention of Physical Inactivity: Childhood Developing Adult Disorders
  52. Public Policy
  53. Conclusion
  54. Acknowledgements
  55. References

12.1 Definitions

12.1.1 Primary aging

Inevitable deterioration of cellular structure and function, independent of disease 240.

12.1.2 Maximal lifespan

Maximum amount of time one member of a species has been observed to survive between birth and death.

12.1.3 Secondary aging

Aging processes which result from disease, bodily abuse, and/or disuse and which are often preventable.

12.1.4 Life expectancy

Average lifespan of a population.

12.1.5 Functional capacity

Absolute maximal value of a function.

12.1.6 Relative functional capacity

Relative age of functional capacity of an organ system, an organ, or cell to its lifetime highest value at a given calendar age.

12.2 Etiology

12.2.1 Primary prevention

The following quotation is impactful because of its source, a report from top exercise scientists that was accepted by the top official of the US Department of Health and Human Services.

The data very strongly support an inverse association between physical activity and all-cause mortality. Active individuals—both men and women—have approximately 30% lower risk of dying during follow-up, compared with inactive individuals. This inverse association has been observed among persons residing in the United States, as well as in other countries, older persons (aged 65 years and older), and persons of different race/ethnic groups. In one study of persons with impaired mobility (unable to walk 2 km and climb 1 flight with no difficulty), physical activity also appeared to be associated with lower all-cause mortality rates 411).”

12.2.2 Less physical activity shortens years of life relative to average lifespan

Healthy behavioral choices in Californian Adventists extend life expectancy by several years, even as much as a decade, 189. Various reports estimate that higher physical activity levels may extend life expectancy relative to average lifespan by 2.1 404, 2.5 394, 5.1 (men) 180, and 5.7 (women) 180 years for the physically active population.

Another example of lifetime physical activity shortening years lived is the increased risk of chronic diseases such as T2D (see Section “Type 2 Diabetes” later in this article). Diagnosis of T2D at the age of 20 years is associated with 17.2 and 17.9 years of life lost in males and females, respectively 365.

12.2.3 Less physical activity increases percentage of population that is disabled

At the same age for death, the high physical-activity group spent less time disabled than the overall population of men (2.5 vs. 3.0 years), while the low physical-activity group actually spends more time disabled than all men (2.6 vs. 1.4 years) 180. Thus, less lifetime physical activity shortens years of life.

12.3 Dose-response relationship between sitting time and prediction of premature death

12.3.1 Longitudinal studies

Katzmarzyk et al. 267 reported a dose-response association existed between sitting time and mortality from all causes and CVD, but not for cancer, independent of leisure time physical activity in 17,000 Canadians, such that hazard ratio was 1.54 for the greatest sitting time. Dunstan et al. 151 found that each 1-h increase in TV viewing time was associated with 11% and 18% increased risks of all-cause and CVD mortality, respectively, in 20,000 Australian men and women. Further, all-cause and CVD mortalities increased 46% and 80%, respectively for TV viewing time more than 4 h/d as compared to less than 2 h/d, which were independent of smoking, blood pressure, cholesterol, diet, waist circumference, and leisure-time exercise.

12.3.2 Mechanisms

While light physical activity is associated with rather low-intensity muscle contractions, it still has favorable improvements on plasma glucose in glucose tolerance tests 227, and differs substantially from the absence of muscle activity while sitting The detrimental effects of sitting have been hypothesized by Stamatakis et al. 488 to occur in the following sequence of events: excessive sitting lowers skeletal muscle blood flow, lowering shear stress on vascular endothelial cells, and decreasing endothelial nitric oxide synthase (NOS) expression. They also noted that the low-grade inflammatory marker, CRP was approximately two times greater in subjects with more than 4 h/d in screen time, compared to those less than 2 h/d. However, 2 weeks of reduced daily stepping 285 and 5 days of bed rest 215 do not increase inflammatory markers so CRP is unlikely to be the first initiating mechanism. Rapid biochemical changes in a rodent models of sitting, hind limb unloading, have demonstrated decreases in rat skeletal muscle protein synthesis rates within the first 6 h 54, 356, 506, 528, 549 and loss of insulin-stimulated glucose uptake into the mouse soleus muscle after 1 day 465.

12.4 Biomarkers of premature death

Low values of functional capacities for maximal aerobic capacity (Vo2max) and for maximal skeletal muscle mass/strength, each alone, are biomarkers for death as they are associated with shorter life expectancies.

12.4.1 Sedentary lifestyle speeds secondary aging of Vo2max by 30 years (illustrated by shifting of age-Vo2max relationship leftward in shown example)

As previously discussed, Vo2max is a measure of CRF. CRF is a health-related component of physical fitness defined as the ability of the circulatory, respiratory, and muscular systems to supply oxygen during sustained physical activity. While physically active and inactive individuals lose a Vo2max at a similar rate (slope of the curve) due to primary aging, the inactive individuals have a leftward shift of the curve. For instance, 80-year-old, physically active women had Vo2maxs that were equivalent to 50-year-old physically inactive women (Fig. 4) 502.

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Figure 4. Best-fit linear lines are shown for aerobic capacities of two cross-sectional groups (aerobic trained and sedentary) as a function of their increasing chronological age. At the chronological age of 80 years, a horizontal line is extended from the endurance-trained line to the left where it intersects the sedentary line at age 50 years. Subjects were women who had been aerobically trained for at least 2 years with road-racing competition (closed circles) versus women who were sedentary (open squares) who performed no regular exercise and had body mass indexes (BMIs) more than 35 kg/m2 (aerobic-trained women were matched across the entire age range for age-adjusted world-best 10-km running times to ensure homogeneity relative competitiveness).

Reproduced, with permission, from reference 502.

12.4.2 Low Vo2max increases prevalence of death

Convincing evidence exists that lower CRF is associated with increased mortality in both men and women, independently of other risk factors 79, 96, 276, 311, 312.

An inverse relationship between CRF and death was present with a cross-sectional comparison between lesser fit men and women with greater fit men and women showed. When CRF in the second lowest CRF quintile is compared to the lowest quantile, the risk of all-cause death in the lowest CRF quantile is increased by 39% and 67% in a prospective study of 40,451 men and 12,831 women, respectively 311 (Fig. 5). Likewise comparing the highest CRF quintile) to the second lowest increased all-cause death risk by 26% and 28% in men and women, respectively. Thus, comparing the top quintile to the lowest quintile increased all-cause death risk by 75% and 113% in men and women, respectively.

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Figure 5. Relative risk of death as a function of cardiorespiratory fitness (CRF) or change in CRF. Relative risks of all-cause mortality by (CRF) quintiles for 12,831 women aged 20 to 100 years without cardiovascular disease (CVD) or cancer in the Aerobics Center Longitudinal Study. Relative risks were adjusted for age, year of examination, body mass index, smoking status, abnormal electrocardiogram, hypertension, diabetes, hypercholesterolemia, and family history of CVD.

Reproduced, with permission, from reference 311.

Changes in CRF level result in a similar change in mortality risk. Men (n = 9777; aged 20-82 at baseline) had two CRF assessments with an average period of 4.9 years between first and second examinations 44, 311. The men were then followed an average of 5.1 years for mortality after the second CRF test. Men who were unfit at both visits had the highest death risk while men who were fit at both visits had the lowest death risk. Remarkably, men who changed fitness status between the two CRF assessments had intermediate risk of death between the fit-that-stayed-fit group and unfit-who-stayed-unfit group. Fit-who-became-unfit between assessments had an increased risk of death. Unfit-men who-became-fit between CRF assessments decreased their risk of death. Erikssen et al. 164 found similar trend and concluded that even small improvements in physical fitness are associated with a significantly lowered risk of death.

12.4.3 Sedentary lifestyle speeds secondary aging of skeletal muscle power by 24 years (illustrated by shifting of age-power relationship leftward in shown example)

Low muscle strength has been inversely associated with all-cause-mortality in 13 studies using subjects more than 65 years of age [see 450 for references]. While, aging causes a similar rate of loss in power between 40 and 90 years of age, untrained, healthy men generate 35% less average power than male competitors at a World Masters Weight-Lifting Championships 401 (Fig. 6). Recreational RT results in strength gains ranging from 10% to 257% after 9-52 weeks of 2-3 days/week RT in subjects mainly aged between 60 and 80 years of age 251; however, a cross-sectional study spanning 20 to 80 years of age in recreational weight-lifters is not available to our knowledge.

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Figure 6. Best-fit linear lines are shown for power of two cross-sectional groups (strength trained and sedentary) as a function of their increasing chronological age. At the chronological age of 80 years, a horizontal line is extended from the power-trained line to the left where it intersects the sedentary line at age 56 years. The cross-sectional strength-trained subjects are shown in closed circles and sedentary in open circles.

Reproduced, with permission, from reference 401.

12.5 Mechanisms

12.5.1 Cardiovascular system

According to Lee et al. 312, several possible biological mechanisms exist for the risk reduction of all-cause mortality in individuals with higher CRF. Higher CRF is associated with healthier values for risk factors including insulin sensitivity, blood lipid and lipoprotein profile, body composition, systemic inflammation, blood pressure, and the autonomic nervous system functioning.

12.5.2 Evolutionary origin

Maximal functional capacity defines the upper limit of a cell, tissue, system, or whole body to maintain homeostasis to stress. Hayflick 225 and others argue that greater functional capacity in vital organs ensures survival, reproductive success, and thus is favored by natural selection. Hayflick lists some stresses that higher capacities in organ systems would be more likely to favor natural selection as

…more efficient healing process, faster sensory responses, or greater strength or speed to avoid predation or natural disasters, finding food, and surviving disease, accidents, and environmental extremes. The favored animals will have developed redundant capacity, or greater physiological reserve, thus increasing chances for survival to reproductive success 225.”

In an extreme stress, such as needing maximal caloric expenditure (reflected in Vo2max) or skeletal muscle strength, animals whose vital systems have the largest redundant functional-capacity would be better able to survive the stress. Thus, the ability to adapt and develop greater physiological capacity in response to repeated stressors (i.e., physical activity) was likely a consequence of natural selection.

12.6 Clinical significance

Low CRF (Vo2max) and handgrip strength predict the risk of impending death. To minimize the all-cause death risk, lifelong efforts, starting in youth, are needed to develop high CRF and skeletal muscle strength within the limitations of one's inherited genes. Slowing of secondary aging of CRF and strength functional capacities can delay the age for inevitable threshold of frailty due to primary aging. A more detailed coverage of inactivity and aging is given in our review in Comprehensive Physiology 50.

13 Prevention of Death by Primary Prevention of Physical Inactivity

  1. Top of page
  2. Organization of Article
  3. Definitions
  4. Overview for Next Three Sections
  5. Summary of Daily Step Reductions from Antiquity
  6. History of Inactivity's Compromising Effects on Function and Health
  7. Cause Versus Treatment
  8. Mechanisms of Physical Inactivity and Activity Differ
  9. Gene-Exercise/Physical Inactivity Interactions
  10. Twin Studies: Modulation of Twin Phenotype by Physical Activity
  11. Variety of Training Types to Primarily Prevent Disease
  12. Diseasome of Physical Inactivity (35 Diseases/Conditions)
  13. Inactivity Accelerates Loss of Functional Capacities with Years of Life
  14. Prevention of Death by Primary Prevention of Physical Inactivity
  15. Metabolic Syndrome
  16. Presentation Strategy for Diseases Composing MS
  17. Obesity
  18. Inactivity Fosters Obese Comorbidities
  19. Insulin Sensitivity/Resistance
  20. Prediabetes
  21. Type 2 Diabetes
  22. Nonalcoholic Fatty Liver Disease
  23. Cardiovascular Diseases: All Types
  24. Presentation of Individual Cardiovascular Diseases
  25. Coronary Heart Disease
  26. Peripheral Arterial Disease
  27. Hypertension
  28. Stroke
  29. Congestive Heart Failure
  30. Known Mechanisms for CVD Risk Factors
  31. Deep Vein Thrombosis
  32. Cognitive Function
  33. Depression and Anxiety
  34. Bone (Osteoporosis)
  35. Osteoarthritis
  36. Balance
  37. Rheumatoid Arthritis
  38. Cancer
  39. Colon Cancer
  40. Breast Cancer
  41. Endometrial Cancer
  42. Activity Prevention of Female Reproductive Disorders
  43. Activity Prevention of Male Reproductive Disorders
  44. Pain
  45. Digestive Tract Diseases
  46. Chronic Respiratory Diseases
  47. Chronic Kidney Disease
  48. Clinical Significance of Physical Inactivity as One Cause of 35 Chronic Conditions
  49. Effectiveness of Drug Therapy for Simultaneous Primary Prevention of 35 Physical Inactivity Conditions
  50. Risk Factors Worsen Over 6 to 12 Months in RCTs
  51. Primary Prevention of Physical Inactivity: Childhood Developing Adult Disorders
  52. Public Policy
  53. Conclusion
  54. Acknowledgements
  55. References

13.1 Etiology

Blair et al. 45 first showed in 1989 that an asymptote exists between METs and age-adjusted mortality rates. Mortality was independent of MET values greater than approximately 9 METs in women and greater than approximately 10 METs in men, but increased when lower than these values.

Kokkinos and Myers found an identical trend in 15,000 older veterans (Fig. 7) 277. An age-related threshold for mortality risk reduction at 4 to 6 METs and an asymptote occurred at approximately 9 METs for women and approximately 10 METs for men (MET values are multiples of resting metabolic rate).

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Figure 7. Mortality risk at different exercise capacities. Significant reductions in mortality do not occur less than 4 metabolic equivalents of resting metabolism (METs), become less at approximately 4 to 6 METs and an asymptote occurring at approximately 10 METs in 15,000 US veterans of wars.

Reproduced, with permission, from reference 277, 279.

Figure 7, shows 20% increase in mortality exists for an individual when maximal exercise MET values grouped between 4.1 and 6.0 METs fall into 2.1 to 4.0 MET group, with no further increase between groupings of MET values smaller than 2.0 METs and 2.1 to 4.0 METs 277. This suggests that a threshold at around 4.0 METs below which, no further increase in mortality exists. Further, an asymptote around 9.0 to 10.0 METs indicates that no differences in mortality risk were reported in comparisons among the higher MET ranges of 10.1 to 12.0, 12.1 to 14.0, and greater than 14.0.

Cautionary statements are necessary though. Maximal MET values decrease ∼10% per decade with aging, in part due to decreased physical activity levels. Thus, physical activity levels need to be maintained or increased to remain in or near to the asymptotic region (> 9 METs) as long as possible with aging.

13.2 Clinical significance

Primary prevention of death (shortening of life expectancy) is possible by increasing CRF.

14 Metabolic Syndrome

  1. Top of page
  2. Organization of Article
  3. Definitions
  4. Overview for Next Three Sections
  5. Summary of Daily Step Reductions from Antiquity
  6. History of Inactivity's Compromising Effects on Function and Health
  7. Cause Versus Treatment
  8. Mechanisms of Physical Inactivity and Activity Differ
  9. Gene-Exercise/Physical Inactivity Interactions
  10. Twin Studies: Modulation of Twin Phenotype by Physical Activity
  11. Variety of Training Types to Primarily Prevent Disease
  12. Diseasome of Physical Inactivity (35 Diseases/Conditions)
  13. Inactivity Accelerates Loss of Functional Capacities with Years of Life
  14. Prevention of Death by Primary Prevention of Physical Inactivity
  15. Metabolic Syndrome
  16. Presentation Strategy for Diseases Composing MS
  17. Obesity
  18. Inactivity Fosters Obese Comorbidities
  19. Insulin Sensitivity/Resistance
  20. Prediabetes
  21. Type 2 Diabetes
  22. Nonalcoholic Fatty Liver Disease
  23. Cardiovascular Diseases: All Types
  24. Presentation of Individual Cardiovascular Diseases
  25. Coronary Heart Disease
  26. Peripheral Arterial Disease
  27. Hypertension
  28. Stroke
  29. Congestive Heart Failure
  30. Known Mechanisms for CVD Risk Factors
  31. Deep Vein Thrombosis
  32. Cognitive Function
  33. Depression and Anxiety
  34. Bone (Osteoporosis)
  35. Osteoarthritis
  36. Balance
  37. Rheumatoid Arthritis
  38. Cancer
  39. Colon Cancer
  40. Breast Cancer
  41. Endometrial Cancer
  42. Activity Prevention of Female Reproductive Disorders
  43. Activity Prevention of Male Reproductive Disorders
  44. Pain
  45. Digestive Tract Diseases
  46. Chronic Respiratory Diseases
  47. Chronic Kidney Disease
  48. Clinical Significance of Physical Inactivity as One Cause of 35 Chronic Conditions
  49. Effectiveness of Drug Therapy for Simultaneous Primary Prevention of 35 Physical Inactivity Conditions
  50. Risk Factors Worsen Over 6 to 12 Months in RCTs
  51. Primary Prevention of Physical Inactivity: Childhood Developing Adult Disorders
  52. Public Policy
  53. Conclusion
  54. Acknowledgements
  55. References

All risk factors for metabolic syndrome (MS) are exasperated by sedentary lifestyle (Fig. 8). In other words, physical inactivity is a primary cause of MS risk factors by virtue of its being upstream to the common MS risk factors. Alternatively, risk factors for MS are secondary to sedentary lifestyle. Consequently, increased physical activity is primary prevention of MS.

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Figure 8. Physical inactivity is an actual cause of premature death by interacting with other environmental factors to increase risk factors for metabolic syndrome, which, in turn produces two “leading causes” of “premature death” (type 2 diabetes and atherosclerosis). Primary prevention of physical inactivity is shown by physical activity inhibiting physical inactivity.

14.1 Disease definition

MS is currently defined as a cluster of three of five risk factors for CVD and T2D, which tend to cluster together in the same individual (Fig. 8) 6. Four of the five factors have drug treatments in attempts to normalize them, and include elevated triglycerides, reduced HDL-cholesterol, elevated blood pressure, and elevated fasting glucose. The fifth factor, elevated waist circumference (as a marker of elevated visceral obesity) does not have as an effective drug treatment. Three abnormal findings of the five risk factors indicate that an individual has MS. In addition, MS is associated with increased risk of certain forms of cancer, polycystic ovarian disease, nonalcoholic fatty liver disease (NAFLD), and neurodegeneration 39.

14.2 Etiology

The total number of US adults who have MS ranges from 77 to 86 million (34.3%-38.5% of total age group) 186. A Joint Scientific Statement indicates that patients with MS have twice the risk of developing CVD and T2D, respectively, over the next 5 to 10 years, as compared to individuals without MS 6. Physical inactivity has been shown to be an important risk factor of MS 38, 185, 295, 559. The proportion of sedentary time, determined by accelerometry was strongly related to metabolic risk, independent of physical activity 22.

14.3 Mechanisms

A 2009 Joint Scientific Statement from the American Heart Association states, “Most persons with the metabolic syndrome have abdominal obesity and insulin resistance. Both of the latter conditions appear to contribute to the development of metabolic risk factors, although the mechanisms underlying these contributions are not fully understood 6.” However, it is understood that physical inactivity is a primary causal mechanism of every MS risk factor—dyslipidemia, hypertension, hyperglycemia, visceral obesity, prothrombsis, and proinflammatory events (Fig. 8).

Several risk factors for MS are associated with physical inactivity, including low-grade inflammation and impaired metabolism 402, 403. Conversely, prevention of physical inactivity through physical activity improves inflammatory markers by reducing resting C-reactive protein (CRP), interleukin-6 (IL-6), and tumor necrosis factor-α concentration 402. On potential mechanism is highlighted by Pedersen 403 who has put forth the hypothesis that the muscle secretome (termed myokines) is involved in mediating some of the health effects of regular exercise, in particular, chronic diseases associated with low-grade inflammation and impaired metabolism, as well as the brain. For example, contracting skeletal muscle during exercise produces interleukin-6, which has anti-inflammatory properties 489.

14.4 Clinical significance of primary prevention of MS

Physical activity is primary prevention for every major MS risk factor. In addition, Bankoski et al. 22 have results that led them to suggest that individuals more than 60 years of age may benefit from reducing total sedentary time and avoiding prolonged periods of sedentary time by increasing the number of light physical activity bouts during sedentary time.

15 Presentation Strategy for Diseases Composing MS

  1. Top of page
  2. Organization of Article
  3. Definitions
  4. Overview for Next Three Sections
  5. Summary of Daily Step Reductions from Antiquity
  6. History of Inactivity's Compromising Effects on Function and Health
  7. Cause Versus Treatment
  8. Mechanisms of Physical Inactivity and Activity Differ
  9. Gene-Exercise/Physical Inactivity Interactions
  10. Twin Studies: Modulation of Twin Phenotype by Physical Activity
  11. Variety of Training Types to Primarily Prevent Disease
  12. Diseasome of Physical Inactivity (35 Diseases/Conditions)
  13. Inactivity Accelerates Loss of Functional Capacities with Years of Life
  14. Prevention of Death by Primary Prevention of Physical Inactivity
  15. Metabolic Syndrome
  16. Presentation Strategy for Diseases Composing MS
  17. Obesity
  18. Inactivity Fosters Obese Comorbidities
  19. Insulin Sensitivity/Resistance
  20. Prediabetes
  21. Type 2 Diabetes
  22. Nonalcoholic Fatty Liver Disease
  23. Cardiovascular Diseases: All Types
  24. Presentation of Individual Cardiovascular Diseases
  25. Coronary Heart Disease
  26. Peripheral Arterial Disease
  27. Hypertension
  28. Stroke
  29. Congestive Heart Failure
  30. Known Mechanisms for CVD Risk Factors
  31. Deep Vein Thrombosis
  32. Cognitive Function
  33. Depression and Anxiety
  34. Bone (Osteoporosis)
  35. Osteoarthritis
  36. Balance
  37. Rheumatoid Arthritis
  38. Cancer
  39. Colon Cancer
  40. Breast Cancer
  41. Endometrial Cancer
  42. Activity Prevention of Female Reproductive Disorders
  43. Activity Prevention of Male Reproductive Disorders
  44. Pain
  45. Digestive Tract Diseases
  46. Chronic Respiratory Diseases
  47. Chronic Kidney Disease
  48. Clinical Significance of Physical Inactivity as One Cause of 35 Chronic Conditions
  49. Effectiveness of Drug Therapy for Simultaneous Primary Prevention of 35 Physical Inactivity Conditions
  50. Risk Factors Worsen Over 6 to 12 Months in RCTs
  51. Primary Prevention of Physical Inactivity: Childhood Developing Adult Disorders
  52. Public Policy
  53. Conclusion
  54. Acknowledgements
  55. References

Each risk factor for MS and chronic diseases resulting from MS will be individually considered next.

16 Obesity

  1. Top of page
  2. Organization of Article
  3. Definitions
  4. Overview for Next Three Sections
  5. Summary of Daily Step Reductions from Antiquity
  6. History of Inactivity's Compromising Effects on Function and Health
  7. Cause Versus Treatment
  8. Mechanisms of Physical Inactivity and Activity Differ
  9. Gene-Exercise/Physical Inactivity Interactions
  10. Twin Studies: Modulation of Twin Phenotype by Physical Activity
  11. Variety of Training Types to Primarily Prevent Disease
  12. Diseasome of Physical Inactivity (35 Diseases/Conditions)
  13. Inactivity Accelerates Loss of Functional Capacities with Years of Life
  14. Prevention of Death by Primary Prevention of Physical Inactivity
  15. Metabolic Syndrome
  16. Presentation Strategy for Diseases Composing MS
  17. Obesity
  18. Inactivity Fosters Obese Comorbidities
  19. Insulin Sensitivity/Resistance
  20. Prediabetes
  21. Type 2 Diabetes
  22. Nonalcoholic Fatty Liver Disease
  23. Cardiovascular Diseases: All Types
  24. Presentation of Individual Cardiovascular Diseases
  25. Coronary Heart Disease
  26. Peripheral Arterial Disease
  27. Hypertension
  28. Stroke
  29. Congestive Heart Failure
  30. Known Mechanisms for CVD Risk Factors
  31. Deep Vein Thrombosis
  32. Cognitive Function
  33. Depression and Anxiety
  34. Bone (Osteoporosis)
  35. Osteoarthritis
  36. Balance
  37. Rheumatoid Arthritis
  38. Cancer
  39. Colon Cancer
  40. Breast Cancer
  41. Endometrial Cancer
  42. Activity Prevention of Female Reproductive Disorders
  43. Activity Prevention of Male Reproductive Disorders
  44. Pain
  45. Digestive Tract Diseases
  46. Chronic Respiratory Diseases
  47. Chronic Kidney Disease
  48. Clinical Significance of Physical Inactivity as One Cause of 35 Chronic Conditions
  49. Effectiveness of Drug Therapy for Simultaneous Primary Prevention of 35 Physical Inactivity Conditions
  50. Risk Factors Worsen Over 6 to 12 Months in RCTs
  51. Primary Prevention of Physical Inactivity: Childhood Developing Adult Disorders
  52. Public Policy
  53. Conclusion
  54. Acknowledgements
  55. References

16.1 Disease definition

The CDC defines overweight for adults as BMIs of 25.0 to 29.9; obese class I as 30.0 to 34.9 BMI; obese class II of 35.0 to 39.9 BMI; and obese class III more than 40.0 BMI. A future auxiliary definition will likely include waist circumference as a proxy for intra-abdominal adipose tissue since all fat is not equally unhealthy.

16.1.1 Etiology

Forty five percent of the US adult population was estimated to be overweight or obese in 1960 to 1962. Overweight and obesity began a continual rise in US adults, aged 20 to 74 years, in the 1980s. The percentage of overweight and obese were 45%, 47%, 56%, 65%, and 66% in survey years 1960 to 1962, 1976 to 1980, 1988 to 1994, 1999 to 2000, and 2003 to 2004, respectively, with men approximately 10% higher than women 88, 386 (Fig. 9). A recent publication establishes that 68% of US adults in 2007 to 2008 are overweight and obese 181.

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Figure 9. Overweight and obese, by age from 1960 to 2006. Modified, with permission, from CDC website (86).

16.2 Misconception that obesity is independent of physical inactivity

The next sections document historical declines in physical activity, putatively reflecting increases physical inactivity.

16.3 Caloric expenditure from physical activity has decreased historically

16.3.1 Caloric expenditure of modern day hunter-gatherers and US Amish versus sedentary

The modern hunter-gatherers’ daily estimated energy expenditures for physical activity are at least 600 kcal more than the average US sedentary adult of today, as documented in column labeled “EE PA” (Table 7) 384. The authors of the data in Table 7 commented, “The systematic displacement from a very physically active lifestyle in our natural outdoor environment to a sedentary, indoor lifestyle is at the root of many of the ubiquitous chronic diseases that are endemic in our culture” 60. Astrand and Rodahl have made a similar comment:

Close to 100% of the biologic existence of our species has been dominated by outdoor activity. Hunting and foraging for food and other necessities in the wilds have been a condition of human life for millions of years—there is obviously no way to revert to our natural way of life—but with insight into our biological heritage we may yet be able to modify our current life. Knowledge of the function of the body at rest as well as during exercise under various conditions is important as a basis for an optimization of our existence 17.”

Table 7. Calories Expended by Physical Activity: Hunter-Gatherer Versus Moderns
SpeciesSexWeight, kgRMR, kcalTEE, kcalRatio (TEE/RMR)EE PA, kcalDay range, km
  1. Abbreviations: RMR, resting metabolic rate; TEE, total energy expenditure; EE PA, energy expenditure attributed to physical activity

    Runner was running at a speed of 12.1 km/h. Table modified from references 115, 384.

Fossil hominids
Homo habitus 48.0140423871.70983 
Homo erectus 53.0151727311.801214 
Homo sapiens 57.0160528801.801284 
Modern hunter-gatherers
KungM46.0127521781.7190310
 F41.0117017701.516008
AcheM59.6154933272.15177816
Acculturated modern humans
Homo sapiens (sedentary office worker)M70.0169420001.183062.4
 F55.0144816791.162312.4
Homo sapiens (runner) 70.0169428881.70119411

Table 1 shows that agrarian Amish men and women undertake 900 and 700 calories worth of daily physical activity, 438. They eat a typical American dieting terms of macronutrients consisting of meat, potatoes, gravy, cakes, pies, and eggs 438. Nonetheless, only 25% and 27% of these Amish men and women, respectively, are overweight; and 0% and 9%, respectively, are obese 438. Several simple observations give rise to conclusions that the lower physical activity levels of modern inactive humans contribute to the obesity epidemic more so than an increase in caloric intake. Agrarian Amish physical activity expenditures exceed modern sedentary by at least 600 kcal/d (Table 1). If modern caloric intake remained unchanged then on average each individual would have a positive energy resulting in 73 pounds of fat per year. Clearly this is untrue and therefore caloric intake must have dropped. However, if the modern population had a decrease in caloric intake of more than 600 kcal/d then obesity rates between Amish and the general population would be similar, which is also untrue. Thus, while caloric intake has dropped between 0 and 600 kcal/d in the general population it is the lack of 600 kcal/d of physical activity has led to a large discrepancy in the obesity rates between the modern general population and Amish societies.

16.3.2 Modern human caloric expenditure is less than free-ranging mammals

Compared to other free-ranging mammals, Hayes et al. 224 calculate that sedentary humans have a significantly lower level of relative physical activity-induced energy expenditure. However, highly active humans have relative physical activity-induced energy expenditure that nears that of other free-ranging mammals (Fig. 10).

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Figure 10. Human caloric expenditure for physical activity in nonathletes is much lower than physically active populations. The y axis is the ratio of activity energy expenditure (AEE)/resting energy expenditure (REE). AEE = free-living energy expenditure – (diet-induced energy expenditure + REE). Data are presented for various human groups (nonathletes living in developed nations, military trainees, individuals from rural areas engaged in high levels of physical activity, and athletes in training) on the x axis. Each bar is a single subject. Nonathletes in developed nations have AEE/REE ratio of approximately 0.5, which is equivalent to physical activity levels (PAL) of approximately 1.67.

Reproduced, with permission, from reference 224].

16.3.3 Decreases by physical activity type in past few decades: United States

A misconception is that leisure time physical activity reflects directional trends of all types of daily physical activity. Brownson et al. 67 reported the following trends in United States (up to 50 years when possible) according to physical activity type: relatively stable or slightly increasing levels of leisure-time physical activity. However, declines occurred in work-related activity, transportation activity, and home-related activity as well as an increase in sedentary activity. Therefore, overall trends for all physical activity types were for declining caloric expenditure by physical activity in recent decade(s).

16.3.4 Decreases by physical activity type in past few decades: China

James 255 shows that transfer from working in the field in China to city work would drop caloric expenditure by approximately 315 kcal/d (men) and approximately 375 kcal/d (women). James comments:

…these calculations are set out to illustrate how foolish it is to focus on only one of the two parts of the energy balance equation. The calculations also illustrate the magnitude of the required drop in intake, given the transformation in our working conditions” 255.

Further, instead of walking to fields, motorized transportation is taken, reducing caloric expenditure by an additional approximately 200 kcal/d. James concludes:

“Thus, intakes may need to fall by 400 to 800 kcal/d for each Chinese adult as their working and living conditions change, and the physical revolution transforms working conditions and transport, with city living and home entertainment with television and cinema viewing taking over from the major sustained demands of an agricultural life 255.”

The misconception of “overnutrition” is due to a widening positive caloric balance due to food intake not falling calorie with calorie to the decline in caloric expenditure (PubMed cites >100,000 papers with the term overnutrition).

16.3.5 Caloric cost of engineering physical activity out of lifestyle

Energy expenditure was significantly greater when daily domestic tasks were performed without the aid of machines or equipment. An estimated 110 kcal/d was estimated to be expended by the combined impact of domestic mechanization 303 (Table 8). The annualization of 110 kcal/d is the caloric equivalent of 11.5 pounds of fat per year. Levine and coauthors concluded, “the magnitude of the energetic impact of the mechanized tasks we studied was sufficiently great to contribute to the positive energy balance associated with weight gain” 303.

Table 8. Estimation of Caloric Cost of Mechanization of Daily Living
 Calories Calories
Active activityusedSedentary activityused
  1. Table modified from reference 303.

Hand clothes washing45Machine clothes washing27
Hand dish washing80Machine dish washing54
Walk to work83Drive to work25
Stair climbing11Elevator3
Total for active219Total for sedentary109

We followed Levine's model and calculated an annualized loss of 64,349 calories (caloric equivalent of 18.4 pounds of fat in 1 year) would not be expended when walking/standing is selected out of lifestyle in our hypothetical model (Table 9).

Table 9. Estimation of Caloric Cost of Removing Walking/Standing from Daily Living
 Calories Calories
Active activityusedSedentary activityused
Walk up one flight of stairs4Take escalator up one flight0.1
Park and walk into fast food restaurant23Sit in car for 10 min in a drive-through lane at restaurant5
Walk dog for 30 min125Let the dog out the back door2
Stand for 30 min of phone calls20Recline for 30 min of phone calls4
Walk into gas station to pay5Pay at pump0.6
Walk 1 min to colleague and stand to talk to them for 4 min6Send e-mail to colleague2
Walk length of two football fields parking away from store10Drive around until a parking space opens near store's entrance3
Total for active193Total for sedentary16.7
16.3.6 Alternative interpretation that physical activity has not declined

Westerterp concluded:

“Physical activity energy expenditure, as measured with doubly labeled water (DLW), has not declined since the start of the obesity epidemic in the 1980s 553. A substantial increase in energy intake has driven the increase in body weight over the past decades.”

Our view of the above quotation follows. Indeed, DLW estimates of energy expenditure determined between 1988 554 and 2006 553 did not significantly differ. However, from approximately 1980 to 1988 the increased prevalence of obesity was already occurring and the slope of the increase remained unchanged through 2006 (Fig. 9). The unchanged slope suggests that whatever was responsible for the increasing prevalence of obesity was maintained, not increased or decreased through 2006. Thus, physical activity levels may have been altered downward prior to 1988 and maintained from 1988 to 2006 at their low levels, which could be one possible explanation for the inconsistency between the DLW results and lack of change in physical activity levels

16.4 Primary prevention of total-body fat gain by physical activity

It is preferable to avoid, in the first place, the excess weight gain that leads to overweight and then obesity. A major emphasis on obesity prevention is needed in the population at large to prevent the development of obesity in those adults who are still in the normal weight range and in successive generations of children and adolescents during development. Treatment will continue to be of critical importance, but treatment alone cannot curb the epidemic; prevention has not been the primary focus 291.”

Minimal research exists on preventing weight gain.

Primary prevention is demonstrated by one human study. A threshold of approximately 60 min a day of moderate-intensity activity throughout a 13-year study was needed to gain less than 2.3 kg in 34,079 healthy US women consuming a usual diet. In a 3-year substudy, the only group having significantly less weight gain than other groups was women whom fit all three of the next criteria: BMI less than 25, moderate-intensity exercise more than 60 min/d, and less than 64 years of age 313.

Primary prevention of further weight gain in already overweight to obese individuals was accomplished with 8 months of low volume-moderate intensity activity (caloric equivalent of walking 12 mile/week at 40%-55% of Vo2max), while high-volume (caloric equivalent of jogging 20 mile/week at 65%-80% of Vo2max) decreased total fat mass by 4.8 kg 479

Primary prevention of weight regain was calculated retrospectively, after 12 months in previously obese female, to be 80 min/d of moderate activity, 35 min/d of vigorous activity, or 0.011 kcal physical expenditure/kg body weight/d 460. Maintenance of a 10% reduced body weight in humans with BMIs more than 30 is associated with a significant decrease in total energy expenditure of approximately 300 to 500 kcal/d greater than that predicted by changes in body mass and composition, which is due predominantly to increased work efficiency of skeletal muscle at low-work intensities 202.

Joyner and Pedersen 259 present another example. Low prevalence of obesity has been related to poor economic conditions. Collapse of the Soviet empire in at the end of the 1980s led to decreased food availability, increased physical activity, and approximately 50% decrease in adult obesity prevalence in Cuba 440. Upon economic recovery, obesity rose 50% from 1993 to 1996.

16.5 Preferential decrease in visceral adipose tissue by exercise

Primary prevention of VAT obesity by physical activity has been demonstrated in numerous human studies. Physical training of T2D patients produced a greater loss in VAT (48%) than subcutaneous adipose tissue (SAT) (18%), did not significantly affect body weight 359. Ross et al. 446 reported that exercise without weight change in obese men reduced VAT more than SAT. Likewise, a greater percentage loss in VAT percentage than in body weight occurred after 12 months in a moderate-intensity exercise intervention study of sedentary, overweight, and postmenopausal women. VAT loss was exercise dose-dependent 252.

A 6-month study examined the dose-response relationship for exercise volume-VAT mass in men and women whose BMI's ranged from 25 to 35 478. Low volume-moderate intensity (caloric equivalent of walking 12 miles/week at 40%-55% of Vo2max) was sufficient to prevent any further gains in VAT mass, while high-volume, high-intensity activity decreased VAT by 6.9% (Fig. 11).

thumbnail image

Figure 11. Gain by visceral and abdominal fat depots in nonexercising group while 6 months of exercise training produced loss in these fat depots. Data are presented as change in (A) visceral abdominal fat, (B) subcutaneous abdominal fat, and (C) total abdominal fat on the y axis. Four exercise levels are given on the x axis; they are (i) control (no exercise); (ii) low-amount, moderate-intensity exercise (caloric equivalent of walking ∼ 12 miles/week at 40% to 55% of peak oxygen consumption); (iii) low-amount, vigorous-intensity exercise (same amount of exercise as group 2, but at 65% to 80% of peak oxygen consumption); and (iv) high-amount, vigorous-intensity exercise (caloric equivalent of jogging ∼20 miles/week at 65% to 80% of oxygen consumption).

Reproduced, with permission, from reference 478.

Remarkably, the nontreatment group (no exercise) had an 8.6% increase in VAT. Extrapolated to 10 years, this would have been a 172% increase in VAT. Slentz et al. 481 later wrote about the nonexercise group, “current levels of physical activity may be so low that significant metabolic deterioration occurs in numerous health-related parameters in as little as 6 months of continued inactivity.” The study provides the evidence that a primary cause of VAT obesity is lack of exercise and that primary prevention for the expansion of VAT is physical activity (Fig. 1).

16.6 Primary prevention of inactivity prevents obesity with predisposed obesity gene

Sedentary lifestyle reveals an obesity phenotype that is primarily prevented by enhanced physical activity.

16.6.1 Humans

The 16% of sedentary adults who are homozygous for the risk allele of AA in rs9939609 in the fat mass and obesity-associated (FTO) gene weighed approximately 3 kg more and had 1.67-fold increased odds of obesity when compared with those not inheriting a risk allele 190. Physically inactive homozygous risk A-allele in rs9939609 carriers had a 2 kg/m2 greater BMI compared with homozygous T-allele carriers in a cross-sectional study of 17,000 Danes 14. A second study replicated the primary preventative effect of physical activity. Adolescents meeting the daily physical activity recommendations overcame the effect of the FTO rs9939609 AA polymorphism on obesity-related BMI, body fat, and waist circumference traits seen in sedentary subjects 449. High physical activity levels in additional studies were associated with attenuated BMI and waist-circumference obesity traits for two additional FTO polymorphisms [rs1861868 421 and rs1121980 542]. Women with the FTO allele rs8050136 only have obesity risk if they are less active 5. In summary then, physical inactivity is required to elicit the phenotype of obesity with polymorphisms predisposing to obesity for the human FTO gene.

16.6.2 Animals

Obesity is primarily prevented in at least two genetically modified, obese rodent models by allowing natural, instinctive voluntary running. Voluntary running prevented obesity and its comorbidities (T2D and NAFLD) with no significant reductions of food intake in cholecytokinin-1 receptor Otsuka Long Evans Tokushima Fatty (OLETF) rats having a mutant cholecystokinin gene 37, 354, 428, 469. Mice lacking expression of the melanocortin-4 receptor (MC4-R) exhibit maturity-onset obesity with hyperphagia, hyperinsulinemia, and hyperglycemia, that is prevented by providing access to wheels for voluntary running 223. Lack of voluntary wheel running reveals the obesity phenotypes.

16.7 Mechanisms

Physical inactivity, as one of the two components in the caloric balance equation, is an actual cause of positive caloric balance, that is, obesity. The most effective control of obesity is primary prevention of physical inactivity by moderate levels of physical activity, rather than secondary or tertiary prevention of obesity associated comorbidities.

16.8 Clinical significance

Physical inactivity is a primary cause to VAT and whole-body obesities. Primary prevention of obesity is possible today for almost all able-bodied individuals able to exercise. According to the CDC primary prevention of overweight/obesity would reduce risks for CHD, T2D, hypertension, dyslipidemia, stroke, NAFLD, gallbladder diseases, sleep apnea and respiratory problems, OA, gynecological problems (abnormal menses and infertility), endometrial, postmenopausal, breast, prostate, and other cancers, and premature death 89.

17 Inactivity Fosters Obese Comorbidities

  1. Top of page
  2. Organization of Article
  3. Definitions
  4. Overview for Next Three Sections
  5. Summary of Daily Step Reductions from Antiquity
  6. History of Inactivity's Compromising Effects on Function and Health
  7. Cause Versus Treatment
  8. Mechanisms of Physical Inactivity and Activity Differ
  9. Gene-Exercise/Physical Inactivity Interactions
  10. Twin Studies: Modulation of Twin Phenotype by Physical Activity
  11. Variety of Training Types to Primarily Prevent Disease
  12. Diseasome of Physical Inactivity (35 Diseases/Conditions)
  13. Inactivity Accelerates Loss of Functional Capacities with Years of Life
  14. Prevention of Death by Primary Prevention of Physical Inactivity
  15. Metabolic Syndrome
  16. Presentation Strategy for Diseases Composing MS
  17. Obesity
  18. Inactivity Fosters Obese Comorbidities
  19. Insulin Sensitivity/Resistance
  20. Prediabetes
  21. Type 2 Diabetes
  22. Nonalcoholic Fatty Liver Disease
  23. Cardiovascular Diseases: All Types
  24. Presentation of Individual Cardiovascular Diseases
  25. Coronary Heart Disease
  26. Peripheral Arterial Disease
  27. Hypertension
  28. Stroke
  29. Congestive Heart Failure
  30. Known Mechanisms for CVD Risk Factors
  31. Deep Vein Thrombosis
  32. Cognitive Function
  33. Depression and Anxiety
  34. Bone (Osteoporosis)
  35. Osteoarthritis
  36. Balance
  37. Rheumatoid Arthritis
  38. Cancer
  39. Colon Cancer
  40. Breast Cancer
  41. Endometrial Cancer
  42. Activity Prevention of Female Reproductive Disorders
  43. Activity Prevention of Male Reproductive Disorders
  44. Pain
  45. Digestive Tract Diseases
  46. Chronic Respiratory Diseases
  47. Chronic Kidney Disease
  48. Clinical Significance of Physical Inactivity as One Cause of 35 Chronic Conditions
  49. Effectiveness of Drug Therapy for Simultaneous Primary Prevention of 35 Physical Inactivity Conditions
  50. Risk Factors Worsen Over 6 to 12 Months in RCTs
  51. Primary Prevention of Physical Inactivity: Childhood Developing Adult Disorders
  52. Public Policy
  53. Conclusion
  54. Acknowledgements
  55. References

17.1 Obesity comorbidities

Risks for the following conditions increase with physical inactivity: Coronary heart disease, T2D, cancers (endometrial, breast, and colon), hypertension, dyslipidemia (e.g., high total cholesterol or high levels of triglycerides), stroke, liver and gallbladder disease, sleep apnea and respiratory problems, OA, and gynecological problems (abnormal menses and infertility).

17.1.1 Death

A recent systemic review by Fogelholm 184 of 36 papers made the next conclusions for the lowering of disease risk with physical activity in obese individuals (conclusions may not apply to BMI > 35). “Poor fitness or low PA in physically unfit individuals is a greater all-cause and cardiovascular mortality risk than obesity in physically fit individual 184.” A study published since the above review essentially concurs with the review by its conclusion made from veterans population that overweight and obese men with moderate CRF fitness had mortality rates similar to those of the highly fit normal-weight reference group 333.

17.2 Clinical significance

Physical inactivity is a cause of some obesity comorbidities. Thus, even if primary prevention for the loss in body fat fails, primary prevention of some, but not all, of obesity's comorbidities is possible with physical activity.

18 Insulin Sensitivity/Resistance

  1. Top of page
  2. Organization of Article
  3. Definitions
  4. Overview for Next Three Sections
  5. Summary of Daily Step Reductions from Antiquity
  6. History of Inactivity's Compromising Effects on Function and Health
  7. Cause Versus Treatment
  8. Mechanisms of Physical Inactivity and Activity Differ
  9. Gene-Exercise/Physical Inactivity Interactions
  10. Twin Studies: Modulation of Twin Phenotype by Physical Activity
  11. Variety of Training Types to Primarily Prevent Disease
  12. Diseasome of Physical Inactivity (35 Diseases/Conditions)
  13. Inactivity Accelerates Loss of Functional Capacities with Years of Life
  14. Prevention of Death by Primary Prevention of Physical Inactivity
  15. Metabolic Syndrome
  16. Presentation Strategy for Diseases Composing MS
  17. Obesity
  18. Inactivity Fosters Obese Comorbidities
  19. Insulin Sensitivity/Resistance
  20. Prediabetes
  21. Type 2 Diabetes
  22. Nonalcoholic Fatty Liver Disease
  23. Cardiovascular Diseases: All Types
  24. Presentation of Individual Cardiovascular Diseases
  25. Coronary Heart Disease
  26. Peripheral Arterial Disease
  27. Hypertension
  28. Stroke
  29. Congestive Heart Failure
  30. Known Mechanisms for CVD Risk Factors
  31. Deep Vein Thrombosis
  32. Cognitive Function
  33. Depression and Anxiety
  34. Bone (Osteoporosis)
  35. Osteoarthritis
  36. Balance
  37. Rheumatoid Arthritis
  38. Cancer
  39. Colon Cancer
  40. Breast Cancer
  41. Endometrial Cancer
  42. Activity Prevention of Female Reproductive Disorders
  43. Activity Prevention of Male Reproductive Disorders
  44. Pain
  45. Digestive Tract Diseases
  46. Chronic Respiratory Diseases
  47. Chronic Kidney Disease
  48. Clinical Significance of Physical Inactivity as One Cause of 35 Chronic Conditions
  49. Effectiveness of Drug Therapy for Simultaneous Primary Prevention of 35 Physical Inactivity Conditions
  50. Risk Factors Worsen Over 6 to 12 Months in RCTs
  51. Primary Prevention of Physical Inactivity: Childhood Developing Adult Disorders
  52. Public Policy
  53. Conclusion
  54. Acknowledgements
  55. References

18.1 Etiology

A summary of the medical literature describing US population-based data on the incidence of 54 endocrine and metabolic disorders in the United States found that the prevalence of impaired fasting glucose and impaired glucose tolerance (IGT) was 26% and 17%, respectively 201. Both of these conditions increase risk for the development of T2D.

18.2 Insulin Effectiveness in Removal of Blood Sugar

This section describes about how successfully blood glucose is lowered by blood insulin.

Insulin insensitivity and resistance is the diminished ability of skeletal muscle and liver cells to respond to the action of a given dose of insulin by transporting glucose from the bloodstream into these tissues, or by reducing glucose production, respectively (B-D in Fig. 12)

thumbnail image

Figure 12. Insulin secretion is presented as a function of insulin sensitivity. Insulin secretion rises as insulin sensitivity falls when physically active individual (Point A) becomes sedentary (Point B). A failure of insulin secretion to compensate for fall in insulin sensitivity is noted when both insulin secretion and insulin sensitivity decline from Points B-C, indicating prediabetes. The upper axis for increased and decreased levels of physical activity implies bidirectionality of the two arrows for glucose intolerance and insulin resistance. The leftward enlarging two arrows illustrate increasing glucose intolerance and insulin resistance with 2 to 3 days of decreased physical activity. The clinical significant is that low levels of physical activity produce a permissive environment for prediabetes. In opposite direction, high levels of daily physical activity markedly diminish the permission state to develop prediabetes. The distinction between the two arrows is based upon variability in Masters athlete's responses to stopping training as shown in Figure 2 of reference 442 in which four subjects had lesser increases in blood insulin (insulin resistance arrow) at 30 min into an oral glucose tolerance test as compared to ten other subjects (glucose intolerance arrow). A continued decline in both insulin secretion and insulin sensitivity at Point D is where overt type 2 diabetes is present.

Reproduced, with permission, from Bergman's original figure in reference 36.

A hyperbolic relationship between insulin sensitivity and insulin secretion has been defined as by Bergman and Ader 36. Figure 12 illustrates the progression from normal glucose tolerance (Point A) to overt clinical T2D (Point D), as described in Harrison's textbook:

…glucose tolerance remains to near-normal (NGT), despite insulin resistance, because the pancreatic beta cells compensate by increasing insulin output (Points A and B). As insulin resistance and compensatory hyperinsulinemia progress, the pancreatic islets in certain individuals are unable to sustain the hyperinsulinemic state. Impaired glucose tolerance, characterized by elevations in postprandial glucose, then develops (Points B and C). A further decline in insulin secretion and an increase in hepatic glucose production lead to overt diabetes with fasting hyperglycemia (Point D). Ultimately, beta cell failure may ensue 417.”

We have further modified Harrisons’ redrawing of Bergman's original figure to indicate that Point A is representative of a daily physically active human and Point B is an occasionally active human. Based on a number of studies, we propose that increases and decreases in daily physical activity over a time frame of hours to a few days places subjects between Points A and B. Thus, daily physical activity prevents the progression to Point B, making it impossible to continue from Point B to Point C and Point D, overt diabetes. Therefore, only if continual physical inactivity is present can the progression to Point C, IGT, and eventually into Point D, overt diabetes, occur. As Zimmet astutely and succinctly wrote, “A large proportion of cases of T2D are preventable” 578.

18.3 Impaired glucose tolerance may increase cardiovascular disease risk

After adjusting for age and sex, an increased risk of cardiovascular disease (CVD) mortality was observed in those with postchallenge hyperglycemia (PCH) and fasting glucose 7.0 mmol/liter or more, with 2-h glucose equal or more than 7.8 and less than 11.1 mmol/liter and fasting glucose less than 7.0 mmol/liter, or with PCH and fasting glucose less than 7.0 mmol/liter 458.

18.4 T2D was preventable 35 to 70 years ago

Diabetes prevalence has risen from 1.4% in 1950 to 7.8% in the United States 366 and from 1% in 1975 to 9.7% in 2007 to 2008 in China 575. Zimmet commented, “In conjunction with genetic susceptibility, particularly in certain ethnic groups, T2D is brought on by environmental and behavioral factors, such as a sedentary lifestyle, overly rich nutrition, and obesity” 578. We will propose the notion that proper volumes of physical activity would essentially primarily prevent most of T2D, as illustrated by maintaining at Point A in Figure 12.

18.5 Inactivity/exercise rapidly change insulin sensitivity

18.5.1 Reduced activity

LaMonte et al. 299 hypothesized that the most proximal behavioral cause of insulin resistance is physical inactivity. Highly endurance trained men's high insulin sensitivity returns to sedentary levels after cessation of training for 38 h 390 or 60 h 72 as measured by euglycemic-hyperinsulimic clamp. Measured 12, 60, and 168 h after the last exercise bout, peripheral tissue glucose disposal dropped from 15.6 to 10.1 to 8.5 mL/kg/min, respectively, compared to 7.8 mL/kg/min in sedentary subjects 72. Similarly, 14, 38, 86, and 144 h after the last exercise bout by endurance trained athletes glucose disposal declined from 9.40 to 7.78 to 6.82 to 7.11 mg/kg/min compared to 6.80 in sedentary subjects 390. Therefore, only days after ceasing exercise training, endurance athletes obtain the same insulin sensitivity as long-term sedentary subjects. Like humans, rats that cease 3 weeks of voluntary wheel running drop their submaximal insulin-stimulated glucose uptake to sedentary values on the second day of no running in skeletal muscle normally recruited during wheel running 292. Less extreme reductions in physical activity, such as humans decreasing daily step numbers from 6203 to 1394 for 1 week lead to a 53% increase in the area under the curve for plasma insulin following an OGTT—a response that occurs due to reduced peripheral insulin sensitivity 388. Conversely, more extreme physical inactivity such as strict bed rest for 24-h/d lasting for 5 days 215, 7 days 46, 341, 494, and 9 days 7 is also associated with substantial increases in insulin resistance. Two days of bed rest did not affect insulin resistance 152.

18.5.2 Increasing activity improves insulin sensitivity in muscle

A single bout of muscle contraction increases insulin sensitivity in perfused hindquarters of healthy animals 241, 254, 433 and in the whole body of healthy humans 229, 342.

Seven days of aerobic training increases whole body insulin sensitivity in 22- and 58-year-old men and women 243, 66-year-old men and women (BMI = 33) 485; 60- to 80-year-old men and women 112, and T2D patients 273, 443. Resistance training also enhances insulin sensitivity and improves glucose tolerance in a wide range of human subjects 525. A systemic review of 20 studies found that supervised RT improved glycemic control and insulin sensitivity in adults with T2D 205.

18.6 Biochemical mechanisms

18.6.1 Exercise-induced glucose uptake into skeletal muscle

A 2009 review wrote, “Within the past 25 years, characterizing the beneficial interaction between acute exercise and subsequent insulin action has been an area of much focus; although progress has been made recently, the underlying mechanisms are still poorly understood” 192.

18.6.2 Animals

Independent of insulin action, exercise acts to prevent hyperglycemia by improving glucose uptake in animal skeletal muscle primarily by independently activating the translocation of glucose transporter, GLUT4, from intracellular locations to the plasma membrane of rats 145, 204, and also by increasing transcription in mice 527 and translation in rats 293 of GLUT4 leading to greater GLUT4 protein content.

18.6.3 Humans

In human subjects, a positive correlation exists between GLUT4 protein content in the vastus lateralis muscle with insulin sensitivity in both sexes 246. The relationship remained in men after adjustment for overall adiposity, regional adiposity, and CRF 246. Endurance-trained healthy individuals have higher GLUT4 mRNA and protein content than sedentary 244, 466. Physical training also increases muscle GLUT4 protein and mRNA in patients with T2D 128. GLUT4 transcription is controlled in part by calcium signaling and the energy sensor 5′-AMP-activated protein kinase (AMPK) during exercise 434, 566, 567.

18.6.4 Skeletal muscle insulin sensitivity with contraction and inactivity

Conversely, much less effort has gone into investigating the mechanisms through which lack of physical activity decreases insulin sensitivity. Although low-grade inflammation can worsen insulin resistance in a variety of models circulating inflammatory markers were unchanged, while insulin resistance increased during 5 days of bed rest, implying that systemic inflammation is not a mechanism for initial insulin resistance 215. Reduced mitochondrial content or dysfunction has also been postulated to cause insulin resistance by leading to an increased accumulation of lipid intermediates in skeletal muscle 456. The lipid intermediates putatively activate serine kinases that reduce insulin signaling ultimately leading to reduced insulin-stimulated GLUT4 translocation to the plasma membrane. However, the links between insulin resistance and an accumulation of lipid intermediates are associative at this time, and an increasing number of reports have found that the relationship does not always hold true 459. Another possibility is oxidative stress. Anderson et al. 13 report that both acute and chronic high-dietary fat intake lead to a dramatic increase in the H2O2-emitting potential of rat or human mitochondria in the absence of any change in respiratory function, consequently generating a shift to a more oxidized cellular redox environment that, if persistent, precedes the development of insulin resistance in skeletal muscle.

Insulin sensitivity in rat epitrochlearis muscle declines at a time (2 days after stopping 3 weeks of voluntary wheel running) when the mitochondrial marker, citrate synthase activity, remains unchanged and elevated from the wheel running 292. No differences in skeletal muscle mitochondria and insulin sensitivity existed between nonobese sedentary controls and hyperphagic, voluntary running in OLETF rats. Rector et al. 429 suggest a constant caloric overload and expanding adiposity may be the primary driver to insulin resistance in the OLETF sedentary animal model. Thyfault 510 suggested “It may be that a hypercaloric/lipidomic environment plus low-energy flux (physical inactivity) is required to induce skeletal muscle insulin resistance in obesity” 510. Inactive skeletal muscles in physically inactive rats have insufficient electron transport flux to completely oxidize mitochondrial intermediates of ß-oxidation, producing lipid toxicity 280, 511. However, acute exercise prior to insulin stimulation can restore insulin-stimulated glucose transport in muscle from obese Zucker rats 512, without improving signaling through the insulin-signaling pathway. Thus, it appears that contraction induces a robust mitochondrial energy flux increasing in a coordinated fashion with both β-oxidation and the trichloroacetic acid (TCA) cycle, that can override existing perturbations of the insulin-signaling pathway to enhanced insulin-stimulated glucose uptake in insulin resistant muscle in obese Zucker rats 511. The links between the contraction-induced energy flux and insulin action are at this time unknown; however, according to a comprehensive review of the topic, the molecule Akt substrate 160 may play an integral role as it is activated by both insulin and muscle contraction and plays a major role in activation of GLUT4 translocation to the plasma membrane 82.

18.7 mRNA mechanisms

Global mRNA analysis of human vastus lateralis muscle identified 4500 transcripts changing after development of insulin resistance following 9 days of continuous bed rest in 20 healthy young men 8. They found that 54% of 162 transcripts in the oxidative phosphorylation pathway decreased. Alibegovic et al. 8 emphasized that they could not exclude the possibility that downregulation of oxidation phosphorylation as well as other genes may have occurred as a result of—not as a causal factor for—skeletal muscle insulin resistance during bed rest. Two potential physiological mechanisms may be decreased capillarization (not determined), as suggested by decreases in both VEGFα mRNA and PGC1α mRNA, or increased fat accumulation due to decreased CPT1B mRNA and thus decreased fatty acid oxidation 8. Furthermore, increased reactive-oxygen species generation and endoplasmic reticulum stress were also identified as potential mechanisms of inactivity-induced insulin resistance 8.

18.8 Clinical significance

Physical inactivity is a primary cause of loss of insulin sensitivity in skeletal muscle, and thus whole body. Primary prevention of almost all of insulin resistance by high levels of daily physical activity is possible for almost all humans up their seventh decade of life 304. Continued long-term reductions in physical activity are a primary cause of insulin resistance.

The clinical consequences of insulin resistance, alone, have been delineated by Reaven 424: Some degree of glucose intolerance/impaired fasting glucose/impaired glucose tolerance (IGT), dyslipidemia [[UPWARDS ARROW] triglycerides, [DOWNWARDS ARROW] HDL-C, [DOWNWARDS ARROW] low-density lipoprotein (LDL) particle size, and [UPWARDS ARROW] postprandial accumulation of triglyceride-rich lipoproteins], endothelial dysfunction ([UPWARDS ARROW] non-nuclear cell adhesion, [UPWARDS ARROW] plasma cellular adhesion molecules, [UPWARDS ARROW] plasma asymmetric dimethylarginine, and [DOWNWARDS ARROW] endothelial-dependent vasodilation), Procoagulant factors ([UPWARDS ARROW] plasminogen activator inhibitor-1 and [UPWARDS ARROW] fibrinogen), hemodynamic factors ([UPWARDS ARROW] sympathetic nervous system activity and [UPWARDS ARROW] renal sodium retention), markers of inflammation ([UPWARDS ARROW] C-reactive protein and [UPWARDS ARROW] white blood cell count) abnormal uric acid metabolism ([UPWARDS ARROW] plasma uric acid concentration and [DOWNWARDS ARROW] uric renal acid concentration), [UPWARDS ARROW] testosterone (ovary), and sleep-disordered breathing. By a direct cause of insulin resistance, physical inactivity indirectly, directly, or both in some cases (endothelial dysfunction) causes all of the aforementioned.

19 Prediabetes

  1. Top of page
  2. Organization of Article
  3. Definitions
  4. Overview for Next Three Sections
  5. Summary of Daily Step Reductions from Antiquity
  6. History of Inactivity's Compromising Effects on Function and Health
  7. Cause Versus Treatment
  8. Mechanisms of Physical Inactivity and Activity Differ
  9. Gene-Exercise/Physical Inactivity Interactions
  10. Twin Studies: Modulation of Twin Phenotype by Physical Activity
  11. Variety of Training Types to Primarily Prevent Disease
  12. Diseasome of Physical Inactivity (35 Diseases/Conditions)
  13. Inactivity Accelerates Loss of Functional Capacities with Years of Life
  14. Prevention of Death by Primary Prevention of Physical Inactivity
  15. Metabolic Syndrome
  16. Presentation Strategy for Diseases Composing MS
  17. Obesity
  18. Inactivity Fosters Obese Comorbidities
  19. Insulin Sensitivity/Resistance
  20. Prediabetes
  21. Type 2 Diabetes
  22. Nonalcoholic Fatty Liver Disease
  23. Cardiovascular Diseases: All Types
  24. Presentation of Individual Cardiovascular Diseases
  25. Coronary Heart Disease
  26. Peripheral Arterial Disease
  27. Hypertension
  28. Stroke
  29. Congestive Heart Failure
  30. Known Mechanisms for CVD Risk Factors
  31. Deep Vein Thrombosis
  32. Cognitive Function
  33. Depression and Anxiety
  34. Bone (Osteoporosis)
  35. Osteoarthritis
  36. Balance
  37. Rheumatoid Arthritis
  38. Cancer
  39. Colon Cancer
  40. Breast Cancer
  41. Endometrial Cancer
  42. Activity Prevention of Female Reproductive Disorders
  43. Activity Prevention of Male Reproductive Disorders
  44. Pain
  45. Digestive Tract Diseases
  46. Chronic Respiratory Diseases
  47. Chronic Kidney Disease
  48. Clinical Significance of Physical Inactivity as One Cause of 35 Chronic Conditions
  49. Effectiveness of Drug Therapy for Simultaneous Primary Prevention of 35 Physical Inactivity Conditions
  50. Risk Factors Worsen Over 6 to 12 Months in RCTs
  51. Primary Prevention of Physical Inactivity: Childhood Developing Adult Disorders
  52. Public Policy
  53. Conclusion
  54. Acknowledgements
  55. References

19.1 Condition's definition

A person with prediabetes has a fasting blood glucose level between 100 and 125 mg/dL and/or 2-h blood glucose between 140 and 199 mg/dL during an OGTT.

19.2 Etiology

It is estimated that 57 million people have prediabetes in the United States (85). Prediabetes is a condition in which blood glucose levels are higher than normal, but not high enough to be classified as T2D. Patients with prediabetes have an increased risk of developing T2D, and T2D's-associated comorbidities of heart disease, and stroke.

19.3 Clinical significance

We speculate that physical inactivity is an actual cause of much of prediabetes cases in those less than 60 years of age. The speculation is based upon the Finnish DPS and DPP RCTs in prediabetics. However, to our knowledge, no large RCTs have been performed to test whether a physically active lifestyle over time primarily prevents prediabetes in healthy individuals as compared to healthy inactive individuals.

20 Type 2 Diabetes

  1. Top of page
  2. Organization of Article
  3. Definitions
  4. Overview for Next Three Sections
  5. Summary of Daily Step Reductions from Antiquity
  6. History of Inactivity's Compromising Effects on Function and Health
  7. Cause Versus Treatment
  8. Mechanisms of Physical Inactivity and Activity Differ
  9. Gene-Exercise/Physical Inactivity Interactions
  10. Twin Studies: Modulation of Twin Phenotype by Physical Activity
  11. Variety of Training Types to Primarily Prevent Disease
  12. Diseasome of Physical Inactivity (35 Diseases/Conditions)
  13. Inactivity Accelerates Loss of Functional Capacities with Years of Life
  14. Prevention of Death by Primary Prevention of Physical Inactivity
  15. Metabolic Syndrome
  16. Presentation Strategy for Diseases Composing MS
  17. Obesity
  18. Inactivity Fosters Obese Comorbidities
  19. Insulin Sensitivity/Resistance
  20. Prediabetes
  21. Type 2 Diabetes
  22. Nonalcoholic Fatty Liver Disease
  23. Cardiovascular Diseases: All Types
  24. Presentation of Individual Cardiovascular Diseases
  25. Coronary Heart Disease
  26. Peripheral Arterial Disease
  27. Hypertension
  28. Stroke
  29. Congestive Heart Failure
  30. Known Mechanisms for CVD Risk Factors
  31. Deep Vein Thrombosis
  32. Cognitive Function
  33. Depression and Anxiety
  34. Bone (Osteoporosis)
  35. Osteoarthritis
  36. Balance
  37. Rheumatoid Arthritis
  38. Cancer
  39. Colon Cancer
  40. Breast Cancer
  41. Endometrial Cancer
  42. Activity Prevention of Female Reproductive Disorders
  43. Activity Prevention of Male Reproductive Disorders
  44. Pain
  45. Digestive Tract Diseases
  46. Chronic Respiratory Diseases
  47. Chronic Kidney Disease
  48. Clinical Significance of Physical Inactivity as One Cause of 35 Chronic Conditions
  49. Effectiveness of Drug Therapy for Simultaneous Primary Prevention of 35 Physical Inactivity Conditions
  50. Risk Factors Worsen Over 6 to 12 Months in RCTs
  51. Primary Prevention of Physical Inactivity: Childhood Developing Adult Disorders
  52. Public Policy
  53. Conclusion
  54. Acknowledgements
  55. References

20.1 Physical activity can reverse prediabetes

While early prediabetes, late prediabetes, and diabetes are in a continuum, they differ in success of primary prevention by physical activity. For instance, daily physical can reverse insulin resistance in healthy individuals (Points B to A in the modified Bergman Fig. 12), and prediabetes (to Point A). However, microvascular (retinopathy, neuropathy, and nephropathy) damage in T2D seems to be nonrepairable by physical activity 417. Thus, the risk of chronic complications that are unable to be reversed by daily physical activity increases as a function of the duration of hyperglycemia, many of which maybe present in individuals when finally diagnosed with T2D 417.

20.2 Etiology

Nearly 24 million people in the United States are diagnosed with T2D in 2007 11. Today the number is likely even higher. By 2020 more than 50% of Americans could have diabetes or prediabetes, at a cost of $3.35 trillion based according to new projections by United Health Group's Center for Health Reform and Modernization 532. The estimated lifetime risk of developing diabetes for babies born in 2000 is 32.8% for males and 38.5% for females, with Hispanics having the highest estimated lifetime risk (males, 45.4% and females, 52.5%) among ethic groups 365, Remarkably, some adolescents have been reported to have T2D in the past 5 years, a disease once called adult-onset diabetes because of its time of onset.

20.3 Primary prevention of T2D: Overview

The CDC Website states that progression to diabetes among those with prediabetes is not inevitable (85). The National Physical Activity Guidelines Advisory Committee Report (NPAGCR) is the major source for disease frequency data in chapter is US government report on physical activity 411. The NPAGCR states that usage of physical activity questionnaires in large prospective cohort and cross-sectional observational studies all show that increased physical activity levels show associations with reduced risk for developing T2D. A systemic review of follow-up, case-control, or cross-sectional studies by Fogelholm 184 concludes for individuals with BMI of 25 to 35 having high BMI even with high physical activity were at a greater risk for the incidence of T2D and the prevalence of cardiovascular and diabetes risk factors, compared with normal BMI with low physical activity. Nonetheless, in men with a BMI of 25 or more, a history of hypertension, a positive parental history of diabetes, or any combination of these factors, the incidence of T2D declined by 41% from the lowest to the highest levels of energy expenditure 233; Table 10).

Table 10. Prospective Studies Implicating Physical Inactivity as a Risk Factor in the Development of T2D
CommentsSample sizeCountry of studyReference
  1. Table modified from Table 1 in reference 538.

[DOWNWARDS ARROW] age-adjusted risk of 6% every 500 kcal of leisure time physical activity5990 menUS233
[DOWNWARDS ARROW] relative risk of 60% between moderately active men and inactive men7735 menUK247
[DOWNWARDS ARROW] relative risk of 26% between upper and lower quintile of physical activity70,102 womenUS405
[DOWNWARDS ARROW] adjusted relative risk of 59% between upper and lower quintile of physical activity2924 menJapan364
[DOWNWARDS ARROW] adjusted relative risk of 15% and 57% between moderate and high compared to low physical activity

2017 men

2352 women

Finland248
[DOWNWARDS ARROW] adjusted relative risk of 13%, 30%, and 76% between low, moderate, and high compared to no physical activity

4069 men

4034 women

Germany337

20.4 Primary prevention of T2D: Exercise clinical trial

Prescribed exercise was associated with a 46% reduction in risk of developing T2D in 110,000 men and women with IGT in Da Qing China over a 6-year intervention period 397.

20.5 Primary prevention of T2D: Lifestyle clinical trial

Prediabetic individuals who incorporate lifestyle modification including increases in their physical activity prevent or delay the onset of T2D by returning their elevated blood glucose levels to normal. During the Finnish Diabetes Prevention Study (Finnish DPS), T2D risk was reduced in prediabetics by 58% 529. In the US Diabetes Prevention Program (DPP), T2D incidence was 11.0, 7.8, and 4.8 cases per 100 person-years in the placebo, metformin, and diet-exercise groups, respectively, with reductions, compared to placebo, of 31% and 58% in metformin, and diet-exercise groups, respectively 275. The result led Knowler et al. 275 to conclude that the lifestyle intervention was significantly more effective than metformin. However, the 58% reduction in the diet-exercise group and 31% reduction with metformin in the Finnish DPS and DPP were both intent-to-treat values. Intent-to-treat values in both studies are the sum of behavioral and biological mechanisms for 100% of the subjects, providing data for physicians on effectiveness of prescription. However, intent-to-treat does not separate behavioral from biological mechanisms. Thus, the biological effectiveness of diet and exercise, independent of behavior, is underestimated due to lower compliance rates in the lifestyle versus metformin groups.

20.6 Physical activity can prevent T2D without weight loss

Primary prevention of T2D without weight loss has major public health importance due to media and medical emphasis on weight loss.

20.6.1 Randomized clinical trials

Subjects were 80% less likely to develop T2D when they did not reach the percentage goal of weight loss, but achieved the goal with respect to exercise volume (more than 4 h/week) as compared to the reference group, in the Finnish DPS 529.

20.6.2 Prediabetes independent of changes in body weight

To determine the effect of leisure-time physical activity on the occurrence of T2D in prediabetics of the Finnish DPS, subjects filled out a 1-year questionnaire for leisure-time activity and then were followed for an additional 4.1 years after the original 3.2-year DPS. Subjects within the upper third of total leisure-time physical activity had approximately 70% lower risk of T2D than those in the lowest third, in overweight, men and women with prediabetes in the Finnish DPS 296, 298, despite similar baseline physical activity, age, baseline BMI and dietary variables and their changes during the study. In the US DPP, a follow-up analysis was made for those subjects who made one goal, but not a second goal. Subjects who met the activity goal (>150 min/week in the US DPP), but did not meet the weight loss goal (>7%), had a 44% reduction in diabetes incidence, independent of the small weight loss (−2.9 kg) that occurred in the DPP 218.

20.7 Mechanisms

A recent review describes available evidence suggesting that exercise primarily acts to lower hyperglycemia by improving glucose sensitivity and mechanisms that interfere directly with endothelial metabolism 4. Another review indicates that it is likely that one of the mechanisms by which physical fitness and activity reduce health risk associated with high BMI is by decreasing fat-to-lean mass ratio and also by decreasing visceral-to-subcutaneous fat ratio. The review indicates that decreasing VAT is particularly important for BMIs between 25 and 30 184. Physical activity also improves glucose-induced insulin secretion in pancreatic β-cells, likely through enhanced gastric inhibitory protein (GIP) secretion 482.

20.8 T2D predisposing genes-environmental interactions

A complex disease such as T2D has, at present, 18 multiple candidate loci that account for only a small percentage (<7%) of the total identifiable genetic load. Snyder at al. wrote:

“Thus, the interpretable genetic contributions that can be identified are quite minor. Presumably, either many low-frequency alleles at different loci contribute to the genetic load or perhaps the many phenotypes are because of other phenomena such as synergistic effects between variants at more than one locus or between different loci and factors in the environment, recurrent spontaneous mutations, or epigenetic defects 483.”

Contemporary hypotheses are that many individual rare gene variants play a much larger role in the genetic predisposition to T2D 435, but currently there is little data to support this speculation.

20.9 Clinical significance

Physical inactivity is an actual cause of insulin resistance and of prediabetes, and therefore, according to disease progression of T2D, itself. T2D is primarily prevented by primary prevention of insulin resistance (prevents movement from Points A to B in the modified Bergman's Fig. 12), and of decreased β-cell insulin secretion and of prediabetes (prevents movement from Points B to C in Bergman's Fig. 12).

T2D is estimated to cost men 11.6 life-years and 18.6 quality-adjusted life-years and women 14.3 life-years and 22.0 quality-adjusted life-years when at the age 40 years 365. Complications given at the American Diabetes Website 11 are: heart disease and stroke (death rate is 2-4 times greater than nondiabetics); hypertension (75% of diabetes); blindness (12,000-24,000 new cases per year); kidney failure (∼ 47,000 new cases per year); neuropathy (60%-70% of diabetics); and lower limb amputation (∼ 71,000 cases per year).

21 Nonalcoholic Fatty Liver Disease

  1. Top of page
  2. Organization of Article
  3. Definitions
  4. Overview for Next Three Sections
  5. Summary of Daily Step Reductions from Antiquity
  6. History of Inactivity's Compromising Effects on Function and Health
  7. Cause Versus Treatment
  8. Mechanisms of Physical Inactivity and Activity Differ
  9. Gene-Exercise/Physical Inactivity Interactions
  10. Twin Studies: Modulation of Twin Phenotype by Physical Activity
  11. Variety of Training Types to Primarily Prevent Disease
  12. Diseasome of Physical Inactivity (35 Diseases/Conditions)
  13. Inactivity Accelerates Loss of Functional Capacities with Years of Life
  14. Prevention of Death by Primary Prevention of Physical Inactivity
  15. Metabolic Syndrome
  16. Presentation Strategy for Diseases Composing MS
  17. Obesity
  18. Inactivity Fosters Obese Comorbidities
  19. Insulin Sensitivity/Resistance
  20. Prediabetes
  21. Type 2 Diabetes
  22. Nonalcoholic Fatty Liver Disease
  23. Cardiovascular Diseases: All Types
  24. Presentation of Individual Cardiovascular Diseases
  25. Coronary Heart Disease
  26. Peripheral Arterial Disease
  27. Hypertension
  28. Stroke
  29. Congestive Heart Failure
  30. Known Mechanisms for CVD Risk Factors
  31. Deep Vein Thrombosis
  32. Cognitive Function
  33. Depression and Anxiety
  34. Bone (Osteoporosis)
  35. Osteoarthritis
  36. Balance
  37. Rheumatoid Arthritis
  38. Cancer
  39. Colon Cancer
  40. Breast Cancer
  41. Endometrial Cancer
  42. Activity Prevention of Female Reproductive Disorders
  43. Activity Prevention of Male Reproductive Disorders
  44. Pain
  45. Digestive Tract Diseases
  46. Chronic Respiratory Diseases
  47. Chronic Kidney Disease
  48. Clinical Significance of Physical Inactivity as One Cause of 35 Chronic Conditions
  49. Effectiveness of Drug Therapy for Simultaneous Primary Prevention of 35 Physical Inactivity Conditions
  50. Risk Factors Worsen Over 6 to 12 Months in RCTs
  51. Primary Prevention of Physical Inactivity: Childhood Developing Adult Disorders
  52. Public Policy
  53. Conclusion
  54. Acknowledgements
  55. References

21.1 Definition

NAFLD is a liver disease in females and males who drink less than 10 and 20 g of alcohol per day, respectively. NAFLD is a progressive disease first apparent by benign fatty liver (steatosis), which can evolve to nonalcoholic steatohepatitis (NASH) that adds inflammation to steatosis. Later progression leads to steatosis with inflammation and mild to advanced fibrosis, to steatosis with fibrosis alone, to cirrhosis and finally to end-stage liver disease. Histological findings of pediatric NAFLD may or may not differ from adult NAFLD 69. Serious outcomes of NAFLD include cirrhosis, hepatocellular carcinoma, CHD, and diabetes 448.

21.2 Etiology

NAFLD is recognized as the leading cause of chronic liver disease in adults and children 517. Prevalence estimates are approximately 20% of adult Americans have benign fatty liver without inflammation or damage and 2% to 5% have NASH 163. Prevalence of NAFLD in a subpopulation of morbidly obese population ranges from 75% to 92%. The prevalence of NAFLD in American children is estimated at 13% 471 and has emerged as the leading cause of chronic liver disease in children and adolescents in the United States 321.

21.2.1 NAFLD independent of changes in body weight

St. Gorge et al. 487 concluded, “maintaining or increasing physical activity provides health benefits for patients with fatty liver, independent of changes in weight.” Caldwell and Lazo 74 contend that increased physical conditioning appears to be closely linked to improved hepatic metabolism independent of changes in body weight.

21.3 Church's findings

Church et al. found lower CRF directly associated with higher NAFLD prevalence in healthy, nonsmoking, nonalcoholic 33 to 73-year-old men 101. A second study reported a low level of habitual physical activity was associated with higher intrahepatic fat content in healthy, nonalcoholic males and females aged 19 to 62 406.

21.4 Interventions/animals

OLETF rats have a spontaneous mutation that inactivates cholecystokinin receptor 1 protein to signal satiety. Without the satiety signal, hyperphagia leads to concurrent obesity and NAFLD between the ages of 5 and 8 weeks old, which progress to T2D 428. Sixteen weeks of voluntary running of 4-week-old OLETF rats totally prevented the development of NAFLD. Morphologically, livers of runners had both fewer and smaller lipid droplets compared nonrunners.

21.5 Cross-sectional studies

Habitual leisure-time physical activity, especially anaerobic, may play a protective role in NAFLD by a reduced rate of abdominal obesity in 24 to 70-year-old human subjects 577. Further, only the association with resistance physical activity remained significant with further adjustment for BMI. Lower Vo2peak was associated with increasing NAFLD activity and with disease severity by NASH diagnosis 282.

21.6 Intervention

Maintaining or increasing physical activity provides health benefits for patients with fatty liver, independent of changes in weight 487. An intensive lifestyle intervention program can successfully produce a 7% to 10% weight reduction and significant improvements in liver chemistry and histological activity in patients with NASH 419. Targeting weight loss by energy restriction alone or in combination with exercise training has been shown to reduce NAFLD pathology. In patients with and without NAFLD, 9 months of diet and exercise intervention led to three important outcomes: (i) reduction in liver fat was approximately twice reduction of VAT; (ii) subjects who resolved NAFLD tended to have higher CRF at prior to the intervention; and (iii) Vo2max at baseline was a predictor of change in liver fat, independently of total and VAT mass 263. The study indicated that CRF fitness and liver fat are related to each other.

21.7 Clinical trials

Long-term RCTs examining the effects of exercise, independent of weight loss, on NAFLD are lacking.

21.8 Mechanisms

Two approaches were tested. The first approach compared OLETF rats with and without 16 weeks of voluntary running. OLETF rats that underwent the voluntary running had 3-fold higher rates of hepatic fatty acid oxidation (complete palmitate oxidization to CO2); lower TG synthesis (70% and 35% lower protein concentrations of fatty acid synthase and acetyl-coenzyme A carboxylase (ACC), respectively], and higher oxidative capacity (35% and 30% higher ACC phosphorylation and cytochrome c concentrations, respectively), as compared to sedentary OLETF rats 428. The second approach was to suddenly cease 16 weeks of daily voluntary running by OLETF rats. The times for hepatic metabolic adaptations to occur with stoppage of running were: 2 days (malonyl-CoA protein increased while phospho-ACC decreased) and 7 days (fatty acid synthase increased and cytochrome oxidase activity and fatty acid oxidation decreased). Thus, reduced physical activity for less than 7 days initiates biochemical sequences that lead to NAFLD in OLETF rats 427.

21.9 Clinical significance

A recent title on PubMed was “Some experts suggest that fatty liver disease will be the next big metabolic disorder associated with obesity and inactivity” 15. Physical inactivity is an actual cause of NAFLD. Most cases of NAFLD can be primarily prevented by sufficient physical activity. Reversal of NAFLD with sufficient physical activity can also occur before hepatofibrosis occurs.

22 Cardiovascular Diseases: All Types

  1. Top of page
  2. Organization of Article
  3. Definitions
  4. Overview for Next Three Sections
  5. Summary of Daily Step Reductions from Antiquity
  6. History of Inactivity's Compromising Effects on Function and Health
  7. Cause Versus Treatment
  8. Mechanisms of Physical Inactivity and Activity Differ
  9. Gene-Exercise/Physical Inactivity Interactions
  10. Twin Studies: Modulation of Twin Phenotype by Physical Activity
  11. Variety of Training Types to Primarily Prevent Disease
  12. Diseasome of Physical Inactivity (35 Diseases/Conditions)
  13. Inactivity Accelerates Loss of Functional Capacities with Years of Life
  14. Prevention of Death by Primary Prevention of Physical Inactivity
  15. Metabolic Syndrome
  16. Presentation Strategy for Diseases Composing MS
  17. Obesity
  18. Inactivity Fosters Obese Comorbidities
  19. Insulin Sensitivity/Resistance
  20. Prediabetes
  21. Type 2 Diabetes
  22. Nonalcoholic Fatty Liver Disease
  23. Cardiovascular Diseases: All Types
  24. Presentation of Individual Cardiovascular Diseases
  25. Coronary Heart Disease
  26. Peripheral Arterial Disease
  27. Hypertension
  28. Stroke
  29. Congestive Heart Failure
  30. Known Mechanisms for CVD Risk Factors
  31. Deep Vein Thrombosis
  32. Cognitive Function
  33. Depression and Anxiety
  34. Bone (Osteoporosis)
  35. Osteoarthritis
  36. Balance
  37. Rheumatoid Arthritis
  38. Cancer
  39. Colon Cancer
  40. Breast Cancer
  41. Endometrial Cancer
  42. Activity Prevention of Female Reproductive Disorders
  43. Activity Prevention of Male Reproductive Disorders
  44. Pain
  45. Digestive Tract Diseases
  46. Chronic Respiratory Diseases
  47. Chronic Kidney Disease
  48. Clinical Significance of Physical Inactivity as One Cause of 35 Chronic Conditions
  49. Effectiveness of Drug Therapy for Simultaneous Primary Prevention of 35 Physical Inactivity Conditions
  50. Risk Factors Worsen Over 6 to 12 Months in RCTs
  51. Primary Prevention of Physical Inactivity: Childhood Developing Adult Disorders
  52. Public Policy
  53. Conclusion
  54. Acknowledgements
  55. References

22.1 Definition

CVD includes all diseases that affect heart and blood vessels. The American Heart Association 320 lists major CVDs as: of subclinical atherosclerosis, CHD, acute coronary syndrome (myocardial ischemia), angina pectoris, stroke (cerebrovascular disease), high blood pressure, congenital cardiovascular defects, cardiomyopathy and heart failure, and other less prevalent CVDs. Physical inactivity increases the prevalence of all major CVDs.

22.2 Known and unidentified risk factors

Of the identified CVD risk factors, modest percentage changes occur with habitual physical activity. Mora et al. 348 indicate that changes in individual risk factors with physical activity are on the order of 5% for blood lipids, 3 to 5 mmHg for blood pressure, and 1% for hemoglobin A1c, in contrast to the large (30%-50%) reductions seen in CVD risk with physical activity.

Mora et al. 348 presented an analysis that showed that almost one-half of risk factors by which physical activity lowers CVDs are not identified. Subjects were 27,000 women compared by more than 1500 kcal/week versus less than 200 kcal/week. Differences in “known” risk factors explained 59.0% of CVD and 36% of CHD of the inverse association between higher physical activity levels and fewer CVD events 348. Respective contributions of known risk factors for CVD and CHD were inflammatory/hemostatic (33% and 21%), blood pressure/hypertension (27% and 15%), traditional lipids (19% and 13%), BMI (10% and 7%), HbA1c/diabetes (9% and 5%), and homocysteine (0.7% and 0.3%) 348. Mora et al. 348 caution that some or all of the aforementioned risk factors have interactions, or are acting in concert, since they add up to more than 59% for CVD and 36% for CHD. The deduction then is 41% and 64% of mechanisms by which physical activity primary prevents CVD and CHD, respectively remained to be identified in 2007.

22.2.1 CVD independent of changes in body weight

Physical activity predicts lower CVD risk independent of obesity 551. BMI's more than 25 contributed only 10% and 7% of physical activity's protection from CVD and CHD, respectively 348. Public health ramifications are that BMI is a minor contributor as to how physical activity prevents CVD and CHD. Increased physical activity levels in women with elevated BMI considerably reduce the risk of CHD 552. However, the risk is not completely eliminated, reinforcing the importance of being lean and physically active 552.

22.3 Unknown pathophysiological mechanisms

Joyner and Green 260 proposed a global hypothesis that might include some, or all, the unknown approximately 40% and 60% of unidentified risk factors by which physical activity reduces CVD and CHD, respectively. Their suggestions for additional risk factor candidates that are improved by habitual physical activity include:

  • Enhanced vagal tone via improved peripheral baroreflex function and central nervous system cardiovascular regulation. In populations, this will be protective and be seen as improved or maintained heart-rate variability.

  • Enhanced or maintained endothelial function that will both favor vasodilatation and contribute to enhanced peripheral baroreflex function by limiting age- or risk factor-associated increases in vascular stiffness.

  • Positive interactions between enhanced endothelial function and sympathetic outflow that limit the effects of high levels of baseline sympathetic outflow on blood pressure 260.

22.4 Coronary vascular disease gene-environmental interaction

CVD is a complex disease. Physical inactivity adaptations in gene expression are very complex, varying by tissue type and time. Thus CVD × physical-inactivity interaction promises to be highly individualized, depending on the degree of accuracy of the desired prediction.

23 Presentation of Individual Cardiovascular Diseases

  1. Top of page
  2. Organization of Article
  3. Definitions
  4. Overview for Next Three Sections
  5. Summary of Daily Step Reductions from Antiquity
  6. History of Inactivity's Compromising Effects on Function and Health
  7. Cause Versus Treatment
  8. Mechanisms of Physical Inactivity and Activity Differ
  9. Gene-Exercise/Physical Inactivity Interactions
  10. Twin Studies: Modulation of Twin Phenotype by Physical Activity
  11. Variety of Training Types to Primarily Prevent Disease
  12. Diseasome of Physical Inactivity (35 Diseases/Conditions)
  13. Inactivity Accelerates Loss of Functional Capacities with Years of Life
  14. Prevention of Death by Primary Prevention of Physical Inactivity
  15. Metabolic Syndrome
  16. Presentation Strategy for Diseases Composing MS
  17. Obesity
  18. Inactivity Fosters Obese Comorbidities
  19. Insulin Sensitivity/Resistance
  20. Prediabetes
  21. Type 2 Diabetes
  22. Nonalcoholic Fatty Liver Disease
  23. Cardiovascular Diseases: All Types
  24. Presentation of Individual Cardiovascular Diseases
  25. Coronary Heart Disease
  26. Peripheral Arterial Disease
  27. Hypertension
  28. Stroke
  29. Congestive Heart Failure
  30. Known Mechanisms for CVD Risk Factors
  31. Deep Vein Thrombosis
  32. Cognitive Function
  33. Depression and Anxiety
  34. Bone (Osteoporosis)
  35. Osteoarthritis
  36. Balance
  37. Rheumatoid Arthritis
  38. Cancer
  39. Colon Cancer
  40. Breast Cancer
  41. Endometrial Cancer
  42. Activity Prevention of Female Reproductive Disorders
  43. Activity Prevention of Male Reproductive Disorders
  44. Pain
  45. Digestive Tract Diseases
  46. Chronic Respiratory Diseases
  47. Chronic Kidney Disease
  48. Clinical Significance of Physical Inactivity as One Cause of 35 Chronic Conditions
  49. Effectiveness of Drug Therapy for Simultaneous Primary Prevention of 35 Physical Inactivity Conditions
  50. Risk Factors Worsen Over 6 to 12 Months in RCTs
  51. Primary Prevention of Physical Inactivity: Childhood Developing Adult Disorders
  52. Public Policy
  53. Conclusion
  54. Acknowledgements
  55. References

The strategy for the presentation of individual cardiovascular diseases follows. The order of CVDs presented will be CHD, peripheral artery disease, hypertension, stroke, and congestive heart failure.

24 Coronary Heart Disease

  1. Top of page
  2. Organization of Article
  3. Definitions
  4. Overview for Next Three Sections
  5. Summary of Daily Step Reductions from Antiquity
  6. History of Inactivity's Compromising Effects on Function and Health
  7. Cause Versus Treatment
  8. Mechanisms of Physical Inactivity and Activity Differ
  9. Gene-Exercise/Physical Inactivity Interactions
  10. Twin Studies: Modulation of Twin Phenotype by Physical Activity
  11. Variety of Training Types to Primarily Prevent Disease
  12. Diseasome of Physical Inactivity (35 Diseases/Conditions)
  13. Inactivity Accelerates Loss of Functional Capacities with Years of Life
  14. Prevention of Death by Primary Prevention of Physical Inactivity
  15. Metabolic Syndrome
  16. Presentation Strategy for Diseases Composing MS
  17. Obesity
  18. Inactivity Fosters Obese Comorbidities
  19. Insulin Sensitivity/Resistance
  20. Prediabetes
  21. Type 2 Diabetes
  22. Nonalcoholic Fatty Liver Disease
  23. Cardiovascular Diseases: All Types
  24. Presentation of Individual Cardiovascular Diseases
  25. Coronary Heart Disease
  26. Peripheral Arterial Disease
  27. Hypertension
  28. Stroke
  29. Congestive Heart Failure
  30. Known Mechanisms for CVD Risk Factors
  31. Deep Vein Thrombosis
  32. Cognitive Function
  33. Depression and Anxiety
  34. Bone (Osteoporosis)
  35. Osteoarthritis
  36. Balance
  37. Rheumatoid Arthritis
  38. Cancer
  39. Colon Cancer
  40. Breast Cancer
  41. Endometrial Cancer
  42. Activity Prevention of Female Reproductive Disorders
  43. Activity Prevention of Male Reproductive Disorders
  44. Pain
  45. Digestive Tract Diseases
  46. Chronic Respiratory Diseases
  47. Chronic Kidney Disease
  48. Clinical Significance of Physical Inactivity as One Cause of 35 Chronic Conditions
  49. Effectiveness of Drug Therapy for Simultaneous Primary Prevention of 35 Physical Inactivity Conditions
  50. Risk Factors Worsen Over 6 to 12 Months in RCTs
  51. Primary Prevention of Physical Inactivity: Childhood Developing Adult Disorders
  52. Public Policy
  53. Conclusion
  54. Acknowledgements
  55. References

24.1 Definition

CHD is a disease of the heart and the coronary arteries that is characterized by atherosclerotic arterial deposits that block blood flow to the heart, causing myocardial infarction.

24.2 Etiology

CHD caused approximately 1 of every 6 deaths (∼ 425,000) in the United States in 2006. In 2010, an estimated 785,000 Americans will have a myocardial infarction, and approximately 470,000 will have a recurrent attack. The American Heart Association recognized physical inactivity as a risk factor for CHD and CVD in 1992 182 and the Surgeon General concluded in 1996, “regular physical activity or CRF decreases the risk of CVD and CHD” 530.

24.3 Primary prevention of CHD

Each 1-MET decrease in maximal aerobic exercise capacity increases the adjusted hazard ratio for death by 12% 278. Using those individuals with 4 MET maximal aerobic exercise capacity as a reference value of 1.0, the mortality risk was 38% lower for those who achieved 5.1 to 6.0 METs, mortality risk declining progressively to 61% for those who achieved more than 9 METs, regardless of age. Unfit individuals who improved their fitness status with serial testing had a 35% lower mortality risk compared with those who remained unfit 278. The NPAGCR reports the literature shows a strong inverse relation between the amount of habitual physical activity performed and CHD morbidity and mortality 411. Sedentary behavior is a major independent risk factor for CHD as middle aged or older individuals of both genders who have moderate or higher amounts of physical activity lower their CHD risk 20% and 30%, respectively, compared to sedentary 411.

24.4 Mechanisms

Positive effects of chronic exercise on primary prevention of CHD could be explained by several mechanisms including: increased nitric oxide and antioxidants, decreased proinflammatory cytokine levels in blood by decreasing production from multiple tissues, and increased regenerative capacity of endothelium expressed by an increased number of circulating endothelial precursor cells, according to a recent comprehensive review of the topic 432. However, these mechanisms do not totally explain the primary prevention of CHD.

24.5 Clinical significance

Physical inactivity is a cause of at least one of three deaths from CHD. Sufficient physical activity primarily prevents CHD.

25 Peripheral Arterial Disease

  1. Top of page
  2. Organization of Article
  3. Definitions
  4. Overview for Next Three Sections
  5. Summary of Daily Step Reductions from Antiquity
  6. History of Inactivity's Compromising Effects on Function and Health
  7. Cause Versus Treatment
  8. Mechanisms of Physical Inactivity and Activity Differ
  9. Gene-Exercise/Physical Inactivity Interactions
  10. Twin Studies: Modulation of Twin Phenotype by Physical Activity
  11. Variety of Training Types to Primarily Prevent Disease
  12. Diseasome of Physical Inactivity (35 Diseases/Conditions)
  13. Inactivity Accelerates Loss of Functional Capacities with Years of Life
  14. Prevention of Death by Primary Prevention of Physical Inactivity
  15. Metabolic Syndrome
  16. Presentation Strategy for Diseases Composing MS
  17. Obesity
  18. Inactivity Fosters Obese Comorbidities
  19. Insulin Sensitivity/Resistance
  20. Prediabetes
  21. Type 2 Diabetes
  22. Nonalcoholic Fatty Liver Disease
  23. Cardiovascular Diseases: All Types
  24. Presentation of Individual Cardiovascular Diseases
  25. Coronary Heart Disease
  26. Peripheral Arterial Disease
  27. Hypertension
  28. Stroke
  29. Congestive Heart Failure
  30. Known Mechanisms for CVD Risk Factors
  31. Deep Vein Thrombosis
  32. Cognitive Function
  33. Depression and Anxiety
  34. Bone (Osteoporosis)
  35. Osteoarthritis
  36. Balance
  37. Rheumatoid Arthritis
  38. Cancer
  39. Colon Cancer
  40. Breast Cancer
  41. Endometrial Cancer
  42. Activity Prevention of Female Reproductive Disorders
  43. Activity Prevention of Male Reproductive Disorders
  44. Pain
  45. Digestive Tract Diseases
  46. Chronic Respiratory Diseases
  47. Chronic Kidney Disease
  48. Clinical Significance of Physical Inactivity as One Cause of 35 Chronic Conditions
  49. Effectiveness of Drug Therapy for Simultaneous Primary Prevention of 35 Physical Inactivity Conditions
  50. Risk Factors Worsen Over 6 to 12 Months in RCTs
  51. Primary Prevention of Physical Inactivity: Childhood Developing Adult Disorders
  52. Public Policy
  53. Conclusion
  54. Acknowledgements
  55. References

25.1 Definition

Narrowed arteries reduce blood flow to limbs, sometimes causing leg pain, generally referred to as claudication when walking.

25.2 Etiology

Peripheral arterial disease (PAD) affects 8 to 12 million people million in the United States (12%-20% > 65 years old have PAD). The NPAGCR concludes that a lack of RCT exercise studies exists to evaluate the effect of exercise training on preventing PAD 411. However, the Report does find support that physical inactivity contributes to accelerated disease progression in those who have PAD. A recent review concludes that the magnitude of effect from a supervised exercise program exceeds that achieved with any of the pharmacologic agents available to treat PAD 387.

25.3 Mechanisms

Mechanisms by which physical activity is primary prevention of PAD are potentially similar to those given for coronary artery disease.

25.4 Clinical significance

Physical inactivity may be a factor increasing the risk of PAD. PAD is a strong predictor of myocardial infraction, stroke, and death due to vascular causes. As atherosclerosis is by far the most common etiology of PAD, and as physical activity primarily prevents coronary artery disease, speculation could be made that physical activity could also primarily prevent PAD. However, insufficient large RCT studies have been performed. Some tertiary preventive evidence exists in PAD patients that walking performed three times or more weekly have less functional decline during the next year 335 and that greater than light physical activity reduces mortality 193 (For cross-reference, see, “Peripheral Circulation”).

26 Hypertension

  1. Top of page
  2. Organization of Article
  3. Definitions
  4. Overview for Next Three Sections
  5. Summary of Daily Step Reductions from Antiquity
  6. History of Inactivity's Compromising Effects on Function and Health
  7. Cause Versus Treatment
  8. Mechanisms of Physical Inactivity and Activity Differ
  9. Gene-Exercise/Physical Inactivity Interactions
  10. Twin Studies: Modulation of Twin Phenotype by Physical Activity
  11. Variety of Training Types to Primarily Prevent Disease
  12. Diseasome of Physical Inactivity (35 Diseases/Conditions)
  13. Inactivity Accelerates Loss of Functional Capacities with Years of Life
  14. Prevention of Death by Primary Prevention of Physical Inactivity
  15. Metabolic Syndrome
  16. Presentation Strategy for Diseases Composing MS
  17. Obesity
  18. Inactivity Fosters Obese Comorbidities
  19. Insulin Sensitivity/Resistance
  20. Prediabetes
  21. Type 2 Diabetes
  22. Nonalcoholic Fatty Liver Disease
  23. Cardiovascular Diseases: All Types
  24. Presentation of Individual Cardiovascular Diseases
  25. Coronary Heart Disease
  26. Peripheral Arterial Disease
  27. Hypertension
  28. Stroke
  29. Congestive Heart Failure
  30. Known Mechanisms for CVD Risk Factors
  31. Deep Vein Thrombosis
  32. Cognitive Function
  33. Depression and Anxiety
  34. Bone (Osteoporosis)
  35. Osteoarthritis
  36. Balance
  37. Rheumatoid Arthritis
  38. Cancer
  39. Colon Cancer
  40. Breast Cancer
  41. Endometrial Cancer
  42. Activity Prevention of Female Reproductive Disorders
  43. Activity Prevention of Male Reproductive Disorders
  44. Pain
  45. Digestive Tract Diseases
  46. Chronic Respiratory Diseases
  47. Chronic Kidney Disease
  48. Clinical Significance of Physical Inactivity as One Cause of 35 Chronic Conditions
  49. Effectiveness of Drug Therapy for Simultaneous Primary Prevention of 35 Physical Inactivity Conditions
  50. Risk Factors Worsen Over 6 to 12 Months in RCTs
  51. Primary Prevention of Physical Inactivity: Childhood Developing Adult Disorders
  52. Public Policy
  53. Conclusion
  54. Acknowledgements
  55. References

26.1 Definition

With prehypertension, SBP is 120 to 139 mgHg and diastolic blood pressure (DBP) is 80 to 89 mmHg. Hypertension is defined as SBP 140 mmHg or more or DBP 90 mmHg or more, or taking antihypertensive medicine.

26.2 Etiology

In the United States, more than 62% of adults have blood pressures above optimal levels. The NPAGCR concluded that both aerobic and progressive resistance exercise cause reduced SBP and DBP in adult humans, although aerobic exercise evidence is stronger 411. The influence of exercise intensity on postexercise hypotension occurred in dose-response fashion such that for each 10% increase in relative Vo2peak, SBP decreased 1.5 mmHg and DBP 0.6 mmHg, thus showing a dose-response relationship for physical activity intensity and lowering of blood pressure postexercise (postexercise hypotension) 156.

26.3 Mechanisms

Eicher et al. 156 suggest potential mechanistic clues for postexercise hypotension involve the renin-angiotensin system and sympathetic nervous systems and include modulation by cardiometabolic, inflammatory, and hemostatic factors.

26.4 Clinical significance

With decreased daily physical activity, increases in SBP and DBP were 2.4 mmHg and 1.6 mmHg, respectively, in normotensive; 3.1 mmHg and 1.7 mmHg in prehypertensive; and 6.9 and 4.9 mmHg in hypertensive subjects, respectively 411. A 3.0-mmHg higher systolic and a 2.3-mmHg higher DBP translates into an estimated 12% increased risk for CHD and 24% increased risk for stroke 415. Physical activity is one of a number of primary preventive measures against hypertension.

27 Stroke

  1. Top of page
  2. Organization of Article
  3. Definitions
  4. Overview for Next Three Sections
  5. Summary of Daily Step Reductions from Antiquity
  6. History of Inactivity's Compromising Effects on Function and Health
  7. Cause Versus Treatment
  8. Mechanisms of Physical Inactivity and Activity Differ
  9. Gene-Exercise/Physical Inactivity Interactions
  10. Twin Studies: Modulation of Twin Phenotype by Physical Activity
  11. Variety of Training Types to Primarily Prevent Disease
  12. Diseasome of Physical Inactivity (35 Diseases/Conditions)
  13. Inactivity Accelerates Loss of Functional Capacities with Years of Life
  14. Prevention of Death by Primary Prevention of Physical Inactivity
  15. Metabolic Syndrome
  16. Presentation Strategy for Diseases Composing MS
  17. Obesity
  18. Inactivity Fosters Obese Comorbidities
  19. Insulin Sensitivity/Resistance
  20. Prediabetes
  21. Type 2 Diabetes
  22. Nonalcoholic Fatty Liver Disease
  23. Cardiovascular Diseases: All Types
  24. Presentation of Individual Cardiovascular Diseases
  25. Coronary Heart Disease
  26. Peripheral Arterial Disease
  27. Hypertension
  28. Stroke
  29. Congestive Heart Failure
  30. Known Mechanisms for CVD Risk Factors
  31. Deep Vein Thrombosis
  32. Cognitive Function
  33. Depression and Anxiety
  34. Bone (Osteoporosis)
  35. Osteoarthritis
  36. Balance
  37. Rheumatoid Arthritis
  38. Cancer
  39. Colon Cancer
  40. Breast Cancer
  41. Endometrial Cancer
  42. Activity Prevention of Female Reproductive Disorders
  43. Activity Prevention of Male Reproductive Disorders
  44. Pain
  45. Digestive Tract Diseases
  46. Chronic Respiratory Diseases
  47. Chronic Kidney Disease
  48. Clinical Significance of Physical Inactivity as One Cause of 35 Chronic Conditions
  49. Effectiveness of Drug Therapy for Simultaneous Primary Prevention of 35 Physical Inactivity Conditions
  50. Risk Factors Worsen Over 6 to 12 Months in RCTs
  51. Primary Prevention of Physical Inactivity: Childhood Developing Adult Disorders
  52. Public Policy
  53. Conclusion
  54. Acknowledgements
  55. References

27.1 Definition

Stroke is a sudden diminution or loss of consciousness, sensation, and voluntary motion caused by rupture or obstruction (as by a clot) of a blood vessel of the brain.

27.2 Etiology

Each year approximately 800,000 individuals experience a new (∼ 610,000) or recurrent (∼ 185,000) stroke with approximately 185,000 deaths in the United States. The most physically active men and women have a 25% to 30% lower risk for stroke incidence and mortality. Data on ischemic and hemorrhagic stroke subtypes is quite limited according the NPAGCR 411. Thirteen of 992 articles satisfied all eligibility criteria to be included in a meta-analysis. Compared with low physical activity, moderate physical activity caused an 11% reduction in risk of stroke outcome and high physical activity a 19% reduction. No significant risk reduction associated with moderate physical activity in women 137. A meta-analysis of 33 prospective cohort studies and 10 case-control studies found that physical activity reduces the relative risk of 0.75 for fatal or nonfatal cerebral infarction, while the corresponding relative risks for cerebral hemorrhage and stroke of unspecified type are 0.67 and 0.71, respectively. The reduction of risk was only statistically significant for men 431.

27.3 Mechanisms

Reimers et al. 431 suggest potential mechanisms of risk reduction by physical activity on stroke. They include: antihypertensive effect, beneficial effect on lipid metabolism, and improved endothelial function [increased endothelial NOS activity and extracellular superoxide dismutase (SOD) expression]. Other mechanisms that may play a role include a lowered blood viscosity, a tendency toward platelet aggregation, increased fibrinolysis, reduced plasma fibrinogen, increased activity of plasma tissue plasminogen activator activity, and higher of HDL cholesterol.

27.4 Clinical significance

Physical inactivity causes deteriorations in multiple mechanisms that cause stroke, as mentioned above. Physical activity could be primary prevention of 10% to 30% of stroke, depending on the volume of activity.

28 Congestive Heart Failure

  1. Top of page
  2. Organization of Article
  3. Definitions
  4. Overview for Next Three Sections
  5. Summary of Daily Step Reductions from Antiquity
  6. History of Inactivity's Compromising Effects on Function and Health
  7. Cause Versus Treatment
  8. Mechanisms of Physical Inactivity and Activity Differ
  9. Gene-Exercise/Physical Inactivity Interactions
  10. Twin Studies: Modulation of Twin Phenotype by Physical Activity
  11. Variety of Training Types to Primarily Prevent Disease
  12. Diseasome of Physical Inactivity (35 Diseases/Conditions)
  13. Inactivity Accelerates Loss of Functional Capacities with Years of Life
  14. Prevention of Death by Primary Prevention of Physical Inactivity
  15. Metabolic Syndrome
  16. Presentation Strategy for Diseases Composing MS
  17. Obesity
  18. Inactivity Fosters Obese Comorbidities
  19. Insulin Sensitivity/Resistance
  20. Prediabetes
  21. Type 2 Diabetes
  22. Nonalcoholic Fatty Liver Disease
  23. Cardiovascular Diseases: All Types
  24. Presentation of Individual Cardiovascular Diseases
  25. Coronary Heart Disease
  26. Peripheral Arterial Disease
  27. Hypertension
  28. Stroke
  29. Congestive Heart Failure
  30. Known Mechanisms for CVD Risk Factors
  31. Deep Vein Thrombosis
  32. Cognitive Function
  33. Depression and Anxiety
  34. Bone (Osteoporosis)
  35. Osteoarthritis
  36. Balance
  37. Rheumatoid Arthritis
  38. Cancer
  39. Colon Cancer
  40. Breast Cancer
  41. Endometrial Cancer
  42. Activity Prevention of Female Reproductive Disorders
  43. Activity Prevention of Male Reproductive Disorders
  44. Pain
  45. Digestive Tract Diseases
  46. Chronic Respiratory Diseases
  47. Chronic Kidney Disease
  48. Clinical Significance of Physical Inactivity as One Cause of 35 Chronic Conditions
  49. Effectiveness of Drug Therapy for Simultaneous Primary Prevention of 35 Physical Inactivity Conditions
  50. Risk Factors Worsen Over 6 to 12 Months in RCTs
  51. Primary Prevention of Physical Inactivity: Childhood Developing Adult Disorders
  52. Public Policy
  53. Conclusion
  54. Acknowledgements
  55. References

28.1 Definition

The heart fails to pump adequate amounts of blood through arteries to tissues, which causes blood to back up and accumulate in other parts of the body, such as lungs and feet. Congestive heart failure (CHF) is often accompanied by distension of the ventricles, peripheral, and pulmonary (causing shortness of breath) edema.

28.2 Etiology

After 65 years of age, approximately 10/1000 individuals have CHF. Hypertension precedes 75% of CHF cases. RCTs for prevention of congestive heart failure are not available. Observational data supports the notion that habitual endurance training is primary prevention against development of CHF.

28.3 Mechanisms

Arbab-Zadeh et al. 16 have concluded that prolonged, sustained endurance training preserves ventricular compliance with aging and may be an important approach to reduce the probability of heart failure with aging. Preservation of ventricular compliance with endurance training probably includes preservation of viscoelastic myocardial properties (absence of increased ventricular stiffening) and eccentric ventricular hypertrophy (a balanced enlargement of ventricular mass and dimensions) 16. These adaptations lead to profoundly improved cardiac performance without apparent change in contractility, which thus is largely explained by enhanced diastolic filling due to low stiffness 16. Together these are coupled with endurance training prevention of arterial stiffening with aging result in preserving ventricular-vascular coupling of compliance, lowering afterload on the left ventricle 16.

28.4 Clinical significance

Physical inactivity contributes development of CHF. Physical activity can primarily prevent some CHF.

29 Known Mechanisms for CVD Risk Factors

  1. Top of page
  2. Organization of Article
  3. Definitions
  4. Overview for Next Three Sections
  5. Summary of Daily Step Reductions from Antiquity
  6. History of Inactivity's Compromising Effects on Function and Health
  7. Cause Versus Treatment
  8. Mechanisms of Physical Inactivity and Activity Differ
  9. Gene-Exercise/Physical Inactivity Interactions
  10. Twin Studies: Modulation of Twin Phenotype by Physical Activity
  11. Variety of Training Types to Primarily Prevent Disease
  12. Diseasome of Physical Inactivity (35 Diseases/Conditions)
  13. Inactivity Accelerates Loss of Functional Capacities with Years of Life
  14. Prevention of Death by Primary Prevention of Physical Inactivity
  15. Metabolic Syndrome
  16. Presentation Strategy for Diseases Composing MS
  17. Obesity
  18. Inactivity Fosters Obese Comorbidities
  19. Insulin Sensitivity/Resistance
  20. Prediabetes
  21. Type 2 Diabetes
  22. Nonalcoholic Fatty Liver Disease
  23. Cardiovascular Diseases: All Types
  24. Presentation of Individual Cardiovascular Diseases
  25. Coronary Heart Disease
  26. Peripheral Arterial Disease
  27. Hypertension
  28. Stroke
  29. Congestive Heart Failure
  30. Known Mechanisms for CVD Risk Factors
  31. Deep Vein Thrombosis
  32. Cognitive Function
  33. Depression and Anxiety
  34. Bone (Osteoporosis)
  35. Osteoarthritis
  36. Balance
  37. Rheumatoid Arthritis
  38. Cancer
  39. Colon Cancer
  40. Breast Cancer
  41. Endometrial Cancer
  42. Activity Prevention of Female Reproductive Disorders
  43. Activity Prevention of Male Reproductive Disorders
  44. Pain
  45. Digestive Tract Diseases
  46. Chronic Respiratory Diseases
  47. Chronic Kidney Disease
  48. Clinical Significance of Physical Inactivity as One Cause of 35 Chronic Conditions
  49. Effectiveness of Drug Therapy for Simultaneous Primary Prevention of 35 Physical Inactivity Conditions
  50. Risk Factors Worsen Over 6 to 12 Months in RCTs
  51. Primary Prevention of Physical Inactivity: Childhood Developing Adult Disorders
  52. Public Policy
  53. Conclusion
  54. Acknowledgements
  55. References

29.1 Endothelial dysfunction

29.1.1 Definition

Endothelial dysfunction is characterized by vascular endothelium exhibiting reduced vasodilation along with greater proinflammatory and prothrombic markers 160.

29.1.2 Conditions associated with endothelial dysfunction

Félétou and Vanhoutte's review states that endothelial dysfunction has been associated not only with hypertension or atherosclerosis, but also with the following long list of conditions:

Since then the term “endothelial dysfunction” has been referred to in the scientific literature more than 20,000 times (PubMed search, November 2005) and has been associated not only with hypertension or atherosclerosis, but also with physiological and pathophysiological processes, including aging, heart and renal failure, coronary syndrome, microalbuminuria, dialysis, thrombosis, intravascular coagulation, preeclampsia, Type I and Type II diabetes, impaired glucose tolerance, insulin resistance, hyperglycemia, obesity, postprandial lipemia, hypercholesterolemia, hyperhomocysteinemia, elevated asymmetric dimethylarginine plasma levels, inflammation, vasculitis, infections, sepsis, rheumatoid arthritis, periodontitis, trauma, transplantation, low birth weight, postmenopause in women, mental stress, sleep apnea syndrome, smoking, nitrate tolerance, glucocorticoids, and so on 179.”

The list of associations would now have to include physical inactivity since the 2005 list is out of date.

29.1.3 Etiology

Sedentary men at ages of 50 to 76 years of age have impaired endothelium-dependent dilation in response to both acetylcholine and increased shear stress in humans 464. In contrast, 50- to 76-year-old, long-term, exercise-trained men do not show age impairment as they have similar endothelium-dependent dilation to acetylcholine-mediated vasodilation as healthy, 22 to 35-year-old men have 132, 166. Regular aerobic exercise can restore the loss of endothelium-dependent vasodilation in previously sedentary 50 to 76-year-old men, implying that physical inactivity is responsible for nearly 100% of endothelial dysfunction in this group of men 132 Seven days of dry immersion, a human model of extreme physical inactivity diminished endothelium-dependent vasodilation by 59% 370.

29.1.4 Clinical outcomes

Davigon and Ganz 121 contend that endothelial dysfunction is an early marker for atherosclerosis and can be detected before structural changes to the vessel wall are evident. If, as claimed by Davigon and Ganz 121, endothelial dysfunction is an early marker for atherosclerosis and can be detected before structural changes to the vessel wall are evident, then a prevention of endothelial dysfunction by a lifetime of physical activity would therefore also prevent most of atherosclerosis reaching a clinical level at the age of 50 to 76 years in men 132, 166 or even initiation of aerobic physical activity within lifestyle 132.

29.1.5 Biochemical adaptations to inactivity

Singularly caged, healthy, young male mice had approximately 30% less endothelium-dependent vasodilation to acetylcholine and approximately 50% less eNOS protein than did five mice in large cages, where the multiple housed mice ran, climbed, and fought during their active cycle 500. With other data, they suggest that an impaired nitric oxide/cGMP-pathway signaling is most likely not involved in endothelial dysfunction induced by a sedentary lifestyle in mice. In a second report, mice in cages without wheels for voluntary running had 148% higher vascular lipid peroxidation, 176% to 188% higher superoxide release, 154% greater NADPH oxidase, and 161% higher rac1 protein than mice voluntarily running in wheels for 6 weeks 306. Expression levels for subunits nox1, p47phox, and p67phox were increased, which suggests increased oxidative stress. A tissue that is not involved in limb movement of running or cycling is the penis. Treadmill training of diabetic rats restored impaired endothelial-dependent and neurogenic nitrergic relaxation in corpus cavernosum 102. The exercise training increased depressed plasma SOD levels of sedentary diabetic rats. The paper hypothesized that nitric oxide bioavailability to corporal smooth muscle was increased by plasma's SOD's antioxidant action.

29.1.6 Mechanisms of inactivity

Lack of shear stress from transient bouts of exercise initiates a cascade of unhealthy events that can be inferred if the sedentary group in exercise studies is considered 307. Extreme 7-day physical inactivity in humans causes microvascular impairment with 32% and 59% decreases in basal flow and endothelium-dependent vasodilation, respectively, that was associated with a selective increase in circulating endothelial microparticles 370, that have procoagulant and proinflammatory properties 99.

29.1.7 Clinical significance

Physical inactivity is a cause of endothelial dysfunction by lack of increased blood flow by exercise in sedentary condition. Exercise signals a beneficial endothelial cell phenotype, at least in part through changes in shear stress and wall stretch in the arteries.

29.2 Atherogenic dyslipidemia

29.2.1 Definition

Atherogenic dyslipidemia is defined as the presence of abnormally low serum concentrations of high-density lipoprotein cholesterol (HDL-C) and elevated concentrations of high triglycerides and small, dense low-density lipoprotein cholesterol (LDL-C).

29.2.2 Etiology

The NPAGCR concludes that habitual physical activity increases serum HDL-C and decreases serum TG. Threshold volumes are from 7 to 15 miles/week of regular aerobic exercise (equating to an approximate 600-800 MET-minutes), with no sex differences 411. The NPAGCR also concludes that evidence is inconsistent as to whether and if LDL-C responds favorably to exercise training. A meta-analysis of 29 RCTs of progressive RT found statistically significant improvements of −2.7% for total cholesterol, −11.6% for ratio of total cholesterol per HDL-C, −5.6% for non-HDL-C, −4.6% for LDL-C, and −6.4% for TG (−8.1 mg/dL, −14.5 to −1.8) 269. The change for HDL-C was not significant. The clinical importance of reductions in LDL-C by RT is that for every 1% reduction in LDL-C levels, a 1% reduction occurs in relative risk for major CHD events.

29.2.3 Clinical significance

Physical inactivity contributes to worsening of atherogenic dyslipidemia. Exercise improves blood lipid values. Lakka and Laaksonen 298 caution not to underestimate the clinical significance of small changes in plasma LDL-C, HDL-C, and TG concentrations with aerobic exercise training because they occur concurrently with benefits on other cardiovascular and metabolic risk factors. Traditional lipids contribute to 19% and 13% of physical activity's contributions of known risk factors to reduce CVD and CHD, respectively, according to Mora et al. 348. Another report found that traditional lipid risk factors account for only 20% of total risk of CVD risk events in 27,000 women 348.

29.3 Hemostasis

29.3.1 Definition

Hemostasis is the arrest of bleeding either by physiological properties of vasoconstriction and coagulation or by surgical means.

29.3.2 Etiology

In a 1990 review, physical inactivity had been associated with the following: low plasma volume, high hematocrit, high plasma fibrinogen, elevated blood viscosity, increased platelet aggregation, and diminished fibrinolysis 157. Low physical fitness and self-reported sedentary lifestyle have been associated with a prothrombotic blood profile in middle-aged women with CHD 363. Plasma levels of the hemostatic factors such as fibrinogen, FVIIag, FVIIa, and vWFag showed an inverse relation to self-reported physical activity. Regular physical exercise has beneficial long-term effects on hemostasis in studies including male subjects [see 363 for reference].

29.3.3 Clinical significance

Numerous reviews suggest that physical activity has long-term healthy benefits on hemostasis 2, 28, 157, 319.

30 Deep Vein Thrombosis

  1. Top of page
  2. Organization of Article
  3. Definitions
  4. Overview for Next Three Sections
  5. Summary of Daily Step Reductions from Antiquity
  6. History of Inactivity's Compromising Effects on Function and Health
  7. Cause Versus Treatment
  8. Mechanisms of Physical Inactivity and Activity Differ
  9. Gene-Exercise/Physical Inactivity Interactions
  10. Twin Studies: Modulation of Twin Phenotype by Physical Activity
  11. Variety of Training Types to Primarily Prevent Disease
  12. Diseasome of Physical Inactivity (35 Diseases/Conditions)
  13. Inactivity Accelerates Loss of Functional Capacities with Years of Life
  14. Prevention of Death by Primary Prevention of Physical Inactivity
  15. Metabolic Syndrome
  16. Presentation Strategy for Diseases Composing MS
  17. Obesity
  18. Inactivity Fosters Obese Comorbidities
  19. Insulin Sensitivity/Resistance
  20. Prediabetes
  21. Type 2 Diabetes
  22. Nonalcoholic Fatty Liver Disease
  23. Cardiovascular Diseases: All Types
  24. Presentation of Individual Cardiovascular Diseases
  25. Coronary Heart Disease
  26. Peripheral Arterial Disease
  27. Hypertension
  28. Stroke
  29. Congestive Heart Failure
  30. Known Mechanisms for CVD Risk Factors
  31. Deep Vein Thrombosis
  32. Cognitive Function
  33. Depression and Anxiety
  34. Bone (Osteoporosis)
  35. Osteoarthritis
  36. Balance
  37. Rheumatoid Arthritis
  38. Cancer
  39. Colon Cancer
  40. Breast Cancer
  41. Endometrial Cancer
  42. Activity Prevention of Female Reproductive Disorders
  43. Activity Prevention of Male Reproductive Disorders
  44. Pain
  45. Digestive Tract Diseases
  46. Chronic Respiratory Diseases
  47. Chronic Kidney Disease
  48. Clinical Significance of Physical Inactivity as One Cause of 35 Chronic Conditions
  49. Effectiveness of Drug Therapy for Simultaneous Primary Prevention of 35 Physical Inactivity Conditions
  50. Risk Factors Worsen Over 6 to 12 Months in RCTs
  51. Primary Prevention of Physical Inactivity: Childhood Developing Adult Disorders
  52. Public Policy
  53. Conclusion
  54. Acknowledgements
  55. References

Deep vein thrombosis (DVT) is the formation of a blood clot (thrombus) in a deep vein. Its prevalence is approximately 12,000 per year with 6% dying within 1 month. DVT is caused by physical inactivity. The lack of shear stress along with low blood flow likely may account for deep vein thrombosis (economy-class syndrome) at the back of vein valves where white cells adhere to fibrin strains 48. The clinical significance of DVT results when a clot breaks off as an embolus and flows to the lung where it blocks a portion of pulmonary blood flow, causing lack of gas exchange in pulmonary capillaries. Primary prevention is muscle pumping from muscle contraction that “squeezes” venous blood to return blood past venous valves back to the right atrium.

31 Cognitive Function

  1. Top of page
  2. Organization of Article
  3. Definitions
  4. Overview for Next Three Sections
  5. Summary of Daily Step Reductions from Antiquity
  6. History of Inactivity's Compromising Effects on Function and Health
  7. Cause Versus Treatment
  8. Mechanisms of Physical Inactivity and Activity Differ
  9. Gene-Exercise/Physical Inactivity Interactions
  10. Twin Studies: Modulation of Twin Phenotype by Physical Activity
  11. Variety of Training Types to Primarily Prevent Disease
  12. Diseasome of Physical Inactivity (35 Diseases/Conditions)
  13. Inactivity Accelerates Loss of Functional Capacities with Years of Life
  14. Prevention of Death by Primary Prevention of Physical Inactivity
  15. Metabolic Syndrome
  16. Presentation Strategy for Diseases Composing MS
  17. Obesity
  18. Inactivity Fosters Obese Comorbidities
  19. Insulin Sensitivity/Resistance
  20. Prediabetes
  21. Type 2 Diabetes
  22. Nonalcoholic Fatty Liver Disease
  23. Cardiovascular Diseases: All Types
  24. Presentation of Individual Cardiovascular Diseases
  25. Coronary Heart Disease
  26. Peripheral Arterial Disease
  27. Hypertension
  28. Stroke
  29. Congestive Heart Failure
  30. Known Mechanisms for CVD Risk Factors
  31. Deep Vein Thrombosis
  32. Cognitive Function
  33. Depression and Anxiety
  34. Bone (Osteoporosis)
  35. Osteoarthritis
  36. Balance
  37. Rheumatoid Arthritis
  38. Cancer
  39. Colon Cancer
  40. Breast Cancer
  41. Endometrial Cancer
  42. Activity Prevention of Female Reproductive Disorders
  43. Activity Prevention of Male Reproductive Disorders
  44. Pain
  45. Digestive Tract Diseases
  46. Chronic Respiratory Diseases
  47. Chronic Kidney Disease
  48. Clinical Significance of Physical Inactivity as One Cause of 35 Chronic Conditions
  49. Effectiveness of Drug Therapy for Simultaneous Primary Prevention of 35 Physical Inactivity Conditions
  50. Risk Factors Worsen Over 6 to 12 Months in RCTs
  51. Primary Prevention of Physical Inactivity: Childhood Developing Adult Disorders
  52. Public Policy
  53. Conclusion
  54. Acknowledgements
  55. References

31.1 Disease definitions

Cognitive function is a broad term defined as the “an intellectual process by which one becomes aware of, perceives, or comprehends ideas. It involves all aspects of perception, thinking, reasoning, and remembering” 357. Cognitive decline is considered an aging disease with two of the most severe forms being Alzheimer's and dementia. Thus, cognitive function can arbitrarily be divided into studies of developing cognition and of primary prevention of the decline in cognition.

31.2 Epidemiology of developing better cognition

Research in exercise and prevention of cognitive decline is relatively new and moving rapidly. Recent reviews exist in references 238, 340.

31.2.1 Lifetime

Aerobic exercise and physical activity improve cognitive health across the lifespan 238. Dutch men, but not women, who were physically active at a young age (15-25 years old), had less of a decline in informational processing capabilities versus individuals physically inactivity early in life 138. Women who reported being physically active at any point in life had a lower likelihood of cognitive impairment in late life 340. Women who began physical activity later in life after inactive teenage years also had lower rates of cognitive impairment in late life. Of the four ages examined, teenage physical activity appeared to be most strongly related to better cognitive function and lower prevalence of cognitive impairment in old age 340.

31.2.2 Children

A 2003 meta-analysis in children (aged 4-18 years) demonstrated a significant positive relationship between physical activity levels and perceptual skills, intelligence quotient, achievement, verbal tests, mathematic tests, and developmental level/academic readiness, with only an effect on memory not found 171. Chaddock et al. 91 found improvements in relational, but not item memory in children. Children who have low physical activity levels have poorer academic achievement scores and inferior cognitive performance as compared to physically fit children 70, 84, 91, 92, 100, 144, 171, 173, 236, 237, 272, 416, 564. A 2008 review concluded that exercise facilitates children's executive function, (i.e., organize thoughts and activities, prioritize tasks, manage time efficiently, and make decisions) similar to improvements reported for other age groups 519.

31.2.3 Adolescents

A cohort study of Swedish men born in 1950 to 1976 who were enlisted for military service at age 18 (N = 1,221,727) 1 reported that cardiovascular fitness, as measured by ergometer cycling, was positively associated with global intelligence scores with aerobic capacity most strongly associated with logic and verbal intelligence. The longitudinal arm of the Swedish study showed that between the ages of 15 and 18 years of age those with the top 10% of improvement in cardiovascular fitness scores had highest enhancement of global intelligence, logical, verbal, visuospatial, and technical scores while those subjects with declines in cardiovascular fitness had less than mean intelligence scores. Further, an association between better cardiovascular fitness at age of 18 years, a higher socioeconomic status, and educational attainment later in life existed.

31.2.4 Older adults

18 RCTs (published prior to 2001) focused on aerobic physical activity interventions in older adults. Aerobic exercise had an overall effect size of 0.48 was found with the largest effect on executive functioning, followed by attention, visuospatial, and speed dependent processes 108. In a prospective study of 18,000 women aged 71 to 80 years, higher levels of long-term regular physical activity were strongly associated with higher levels of cognitive function and a 20% lower risk of cognitive impairment 555. Physical inactivity (less than three bouts of exercise per week) increased the risk of dementia from 13.0 per 1000 person-years to 19.7 per 1000 person-years 305. Each ten blocks that were walked per day in women more than 65 years old resulted in 13% less impairment in cognitive function 573. Moderate and high levels of physical activity were associated with significantly lower risks for Alzheimer disease and for dementia of any type 308. An inverse relationship between physical activity levels and dementia was found in men and women aged 65 years and older 412. Higher Vo2peak was associated positively with preservation of cognitive function over a 6-year period in 349 subjects over the age of 55 24.

Increased aerobic fitness can be neuroprotective and can enhance cognitive function 108, 110, 281. Kramer et al. reported in 1999 that those who received aerobic training (walking) showed substantial improvements in performance on tasks requiring executive control compared with stretching- and toning-trained subjects aged 60 to 75 years 281. Resistance exercise also had a positive impact on cognitive function in 65 to 75-year-old males 83.

31.2.5 Physical activity, not fitness, improves cognitive function

A meta-analysis was performed on 571 fitness effect sizes from 1306 subjects from 37 studies prior to 2005. Etnier et al. 171 concluded that the empirical literature did not support a relationship between aerobic fitness and cognitive performance. Rather across the same 37 studies designed to test the effects of fitness on cognition, the summary statistic indicated that a positive association existed between physical activity and cognitive performance 171, confirming the findings of three previous meta-analytic reviews of this literature 108, 172, 472.

31.2.6 Dementia: Primary prevention

The NPAGCR [see 411 for references)] found that physical activity delayed the onset of cognitive decline or dementia in most studies with sample sizes greater than 1000 individuals, but with inconsistent findings for underpowered studies containing low subject numbers. Nine of 16 prospective studies had odds ratios (OR = 0.63) showing protection by physical activity from dementia or Alzheimer's disease [Figure G8.8 in NPAGCR 411]. To date, no RCT has been performed to show that regular physical activity prevents dementia 444.

31.3 Mechanisms

As a new frontier in inactivity disease, we chose to provide a more extensive presentation on the inactivity/exercise mechanisms for cognitive function.

31.3.1 Physiological/structural
31.3.1.1 Human

Highly cardiorespiratory-fit or aerobically trained individuals had reduced activation of the anterior cingulated cortex concomitantly with lower indecision that arises when multiple conflicting responses are elicited in response to a stimulus during a task that required variable amounts of executive control, relative to untrained individuals 110. Fit and trained subjects also had greater task-related activity in regions of the prefrontal and parietal cortices that are involved in spatial selection and inhibitory functioning 110.

Reductions in hippocampus volume are associated with a decline in memory performance, specifically acquisition and recall measures 409 hippocampal volume is positively correlated with physical fitness in adults 162 and children 10-year old 91, and can be increased by aerobic training of both schizophrenic and healthy subjects 396. Likewise, a 6-month aerobic exercise intervention increased gray matter volume in the frontal and superior temporal lobes 109. Further, results suggest that aerobic fitness does not have a general impact on the volume of all structures in the brain in children 92. Electrical function is increased in “high” hit older (50 to 62-year-old) adults 154 in potentially due to increased synaptic plasticity and long-term-potentiation 543.

31.3.1.2 Animal

Exercise increases neurogenesis in the dentrate gyrus, a hippocampal region that is important for spatial recognition. van Praag et al. 534 showed increased voluntary exercise is sufficient for enhanced survival of newborn cells in 3-month-old adult mouse dentate gyrus. Another study found that improved spatial pattern separation in 3-month-old mice was tightly correlated with increased neurogenesis and vasculature in the dentate gryus after 10 weeks of voluntary wheel running 117. Rat voluntary runners have longer-lasting long-term potentiation (LTP) following tetanic stimulation (due to lower threshold of LTP induction) in dentate gyrus, which is dependent upon the activation of N-methyl-d-aspartate (NMDA) receptors 537. Another anatomical change associated with improved cognitive is improvements is brain blood flow. Voluntary wheel running can increase blood vessel density, blood flow, and capillary perfusion of the motor cortex in rats 42, 501. Potential mechanisms include the increased density of microvessels 141, angiopoietin 1 141, VEGF protein 141, or endothelial proliferation 141, 159. Angiogenesis in the brain is associated with enhanced improvement in a functional outcome like water maze time 535, but not the ability to activate the motor limbs 274.

31.3.2 Biochemical adaptations
31.3.2.1 Human

The human brain is responsible for approximately 70% to 80% of circulating Brain-derived neurotrophic factor (BDNF) at rest 422. BDNF mRNA and protein expression were increased in human skeletal muscle after exercise, but muscle-derived BDNF appeared not to be released into the circulation 331.

31.3.2.2 Animal

Physical activity can induce local and systemic expression of many growth factors that protect the brain from physical inactivity-related declines in function. BDNF plays an important role in the growth, development, maintenance, and function of several neuronal systems 371. BDNF mRNA was upregulated in a dose-response manner following 2, 4, and 7 days of voluntary distance run by rats 371. Three days of voluntary wheel running had as much effect as 28 days in increasing mRNAs for growth factors (BDNF, neural growth factor, and fibroblast growth factor-2), synapse-related proteins (synapsin, syntaxin, and synaptoginamin), neurotransmitter systems [reduced γ-aminobutyric acid (GABA) neurogenic signaling, which is associated with increased recover], and intracellular kinases (Ca2+ /calmodulin-dependent protein kinase II, MAPK/ERK kinase 1/2, and mitogen-activated protein kinase 1/2) 345. Whether 1 day would have the same effects is unknown. Conversely, cessation of voluntary wheel running in spontaneously hypertensive rats can decrease the BDNF and BDNF/NT-3 growth factor receptor (TrkB) system mRNA in hippocampus for a duration lasting at least 10 days 558.

Another critical growth factor for neuroprotection and brain health is IGF-1. A number of studies show that IGF-1 increases in the brain following exercise. Infusion of IGF-1 mimicked the effects of exercise, while infusion of an anti-IGF-1 antibody blocked the effects 80. Blocking hippocampal IGF-I receptors abolished the effect of exercise on augmenting recall in rats during 5 days of wheel running 140. Anti-IGF-I antibody can also abrogate the protective effects of exercise in many types of brain lesions 81. Like BDNF, the levels of IGF-1 increase in the circulation in response to physical activity 520 and both exercise and systemic infusion of IGF-1 increases new and survivability of BrdU+ cells in the hippocampus 322, 520, likely signaling through IGF receptors located on the luminal side of the brain 322. In culture, IGF stimulates VEGF via hypoxia-inducible factors (HIF) mechanism 322. Blockage of peripheral VEGF prevents the increase in BrdU+ cells and mitosis in immature neurons of exercising animals only 174.

31.3.3 Genetic
31.3.3.1 Human

Polymorphisms in the APOE4 genotype have been examined in relationship to physical activity, with mixed results 398. For instance in cross-sectional studies examining physical activity by questionnaire, two studies suggest that carriers of APOE4 benefit from physical activity 127, 461, while one does not 412. However, higher aerobic fitness levels in older women having the APOE4 genotype had better cognitive function in another cross-sectional study 170, suggesting that physical activity levels that are capable of increasing aerobic fitness are needed to improve cognitive function in those with APOE4 genotypes.

31.3.3.2 Animal

Animal studies support this. Mice with the APOE4 genotype that voluntarily ran in wheels for 6-month rescued cognitive function and BDNF levels within the hippocampus by returned them to that found in APOE3 (control) mice 378.

31.4 Clinical significance

Epidemiological, interventions, and mechanistic insights from human and rodent studies all suggest that physical inactivity can accelerate declines in cognitive function; a decline that be attenuated or potentially reversed by physical activity. However, questions remain regarding the best practice for mode, duration, intensity, the long-lasting effects, potential gender-specific effects, and the interaction with genetic components.

32 Depression and Anxiety

  1. Top of page
  2. Organization of Article
  3. Definitions
  4. Overview for Next Three Sections
  5. Summary of Daily Step Reductions from Antiquity
  6. History of Inactivity's Compromising Effects on Function and Health
  7. Cause Versus Treatment
  8. Mechanisms of Physical Inactivity and Activity Differ
  9. Gene-Exercise/Physical Inactivity Interactions
  10. Twin Studies: Modulation of Twin Phenotype by Physical Activity
  11. Variety of Training Types to Primarily Prevent Disease
  12. Diseasome of Physical Inactivity (35 Diseases/Conditions)
  13. Inactivity Accelerates Loss of Functional Capacities with Years of Life
  14. Prevention of Death by Primary Prevention of Physical Inactivity
  15. Metabolic Syndrome
  16. Presentation Strategy for Diseases Composing MS
  17. Obesity
  18. Inactivity Fosters Obese Comorbidities
  19. Insulin Sensitivity/Resistance
  20. Prediabetes
  21. Type 2 Diabetes
  22. Nonalcoholic Fatty Liver Disease
  23. Cardiovascular Diseases: All Types
  24. Presentation of Individual Cardiovascular Diseases
  25. Coronary Heart Disease
  26. Peripheral Arterial Disease
  27. Hypertension
  28. Stroke
  29. Congestive Heart Failure
  30. Known Mechanisms for CVD Risk Factors
  31. Deep Vein Thrombosis
  32. Cognitive Function
  33. Depression and Anxiety
  34. Bone (Osteoporosis)
  35. Osteoarthritis
  36. Balance
  37. Rheumatoid Arthritis
  38. Cancer
  39. Colon Cancer
  40. Breast Cancer
  41. Endometrial Cancer
  42. Activity Prevention of Female Reproductive Disorders
  43. Activity Prevention of Male Reproductive Disorders
  44. Pain
  45. Digestive Tract Diseases
  46. Chronic Respiratory Diseases
  47. Chronic Kidney Disease
  48. Clinical Significance of Physical Inactivity as One Cause of 35 Chronic Conditions
  49. Effectiveness of Drug Therapy for Simultaneous Primary Prevention of 35 Physical Inactivity Conditions
  50. Risk Factors Worsen Over 6 to 12 Months in RCTs
  51. Primary Prevention of Physical Inactivity: Childhood Developing Adult Disorders
  52. Public Policy
  53. Conclusion
  54. Acknowledgements
  55. References

32.1 Definitions

32.1.1 Depression

A mood disorder marked especially by sadness, inactivity, difficulty with thinking and concentration, a significant increase or decrease in appetite and time spent sleeping, feelings of dejection and hopelessness, and sometimes with suicidal thoughts or an attempt to commit suicide.

32.1.2 Anxiety

An abnormal and overwhelming sense of apprehension and fear often marked by physiological signs (as sweating, tension, and increased pulse), by doubt concerning the reality and nature of the threat, and by self-doubt about one's capacity to cope with it.

32.2 Etiology

Depression is relatively common affecting 8% of women and 4% of men, having a lifetime prevalence of 16%, and an annual cost of $83 billion in the United States 207. Anxiety is prevalent in 10% of the general public, has many similar symptoms and treatments to depression, but can also include a wide range of phobias. Both depression and anxiety are associated with increased risks of many other diseases. Genetic, biological, chemical, hormonal, environmental, psychological, and social factors all likely intersect to contribute to depression in women [see 368 or details]. Some of these same factors play a role in men. For anxiety, disorders last at least 6 months and commonly occur along with other mental or physical illnesses, including alcohol or substance abuse.

Since 1995, more than 100 population-based observational studies have been completed. Looking at these studies, the 2008 NPAGCR 411 concluded that active people were nearly 45% less likely to have depressive symptoms than inactive people. Looking at the 28 prospective cohorts allows for examination of physical activity levels before depression symptoms occur. Nearly 4 years of physical inactivity increased risk for depression by about 49% without adjustment for depression risk factors and by 22% after adjusting for known risk factors such as age, sex, race, education, income, smoking, alcohol use, and chronic health conditions. In 66 of 67 cohort studies, physical inactivity increased the risk of depression. While many of the studies relied on self-questionnaires, eight cohort studies contained clinical diagnosis of depression symptoms, which reported an increase of 40% in the inactive group. Physical working capacity was found in depressed male patients but not female patients 350. Morgan noted that both grip strength inversely related to hospital length stay and lower in depressed patients 349. In Britain, children under the age of 15 had an 8% reduction in depression symptoms for every hour of exercise completed per week 447. Likewise, lower fitness was found in depressed male patients but not female patients 350.

Treatment of depression with exercise has also been shown to be effective. In 1979, Greist et al. 210 found that running and time-limited/unlimited psychotherapy reduced depression symptoms similarly. Depressed patients that participated in exercise had less of a need for medication and less relapse 18, and adhere to exercise (66%) greater than medication (40%). An exercise dose consistent with public health recommendations in 1998 to 2001 (about 12 miles/week of walking for 12 weeks) reduced depressive symptoms 47% from baseline while a lower dose exercise (5 mile/week) group did not respond any better than the exercise placebo control group 150. Other studies have found a relatively quick effect of exercise involving 10 days of walking for 30 min/d resulted in a decrease in the Hamilton Rating Scale for Depression and self-assessed intensity of symptoms 139.

The NPAGCR 411, 531 concluded that after examining four population-based cross-sectional studies of over 121,000 Americans that regular physical activity decreases the odds of an anxiety disorder. Specifically, the National Co-Morbidity Study found physical inactivity increased anxiety disorder by 1.75 times in raw odds and 1.38 times once adjusted for sociodemographic and illness 203. Australians reporting no activity were 2.1 times more likely to develop anxiety disorders than those conducting more than 3 h of vigorous activity a week 30; similar results were found in inactive young Germans 492. In summary of all random controls trials the Committee Report concluded a strong effect of a moderate (> 25 min/d) amount of physical activity (both resistance and aerobic) in reducing anxiety symptoms.

32.3 Mechanisms

32.3.1 Physiological

A decline in cognitive function may be a cause of depression. For instance, in over 5000 elderly women (mostly white), increasing symptoms of depression were associated with reduced cognitive function in each of three tests, showing a negative correlation 574. Those with six cognitive-impairment symptoms had a relative risk of 2.3 times to be depressed than those with 0 to 2 impairments. While it is unknown whether the mechanisms of increased depression and decreased cognitive function are similar in different populations (e.g., young vs. old), reduced brain tissue, blood flow, or otherwise are found in both suggesting a similar cause if not similar mechanism.

32.3.2 Biochemical adaptations
32.3.2.1 Human

Potential roles of elevated gluccocorticoids due to a failure to suppress the hypothalamic-pituitary-adrenal (HPA) axis have also been studied in healthy humans. Physically active individuals have less stress response to the same absolute exercise in terms of cortisol release 323. Furthermore, the most fit group had a diminished release of cortisol in response to intravenous ovine corticotropin-releasing hormone 323.

32.3.2.2 Animal

In rats, physical inactivity increases the adrenocorticotrophic hormone (ACTH) levels rather than cortisol in response to a stressor 143, 177. However, questions remain about the level of physical activity necessary for beneficial HPA adaptations with some studies suggesting intense physical activity can have a detrimental effect 97.

Changes in monoamines and other circulating markers may also be involved in inactivity-induced increases in depression and anxiety, similar to changes in cognitive function. Catecholamines, specifically norepinephrine (NE) signaling and production, is increased with physical activity in the pons medulla, which is where the only NE-producing nerves are found that serve the frontal cortex, hippocampus, thalamus, and cerebellum; a major source of NE-serving nerves to the hypothalamus, amygdala, and spinal cord [reviewed in reference 142]. A decrease in NE levels in response to repeated stress is prevented by chronic voluntary wheel running (VWR) in rats 142, with a threshold of as little as 30 min/d of VWR 149. In addition to increased NE levels at the site of production, microdialysis showed increased levels and turnover of NE where the neurons terminate in the spinal cord is found after just 1 h of treadmill running in rats 395.

Levels of 5-hydroxytryptamine (serotonin), an important neurotransmitter for mood, and its receptor are potentially increased by acute treadmill running due to the increased lipolysis and free fatty acids (FFA) binding to albumin. By reducing albumin, tryptophan levels are higher in circulation and have an increased entry into the brain, leading to increased synthesis of serotonin 95.

32.3.3 Genetic
32.3.3.1 Human

In a large twin-population based in the Netherlands, data about leisure-time exercise and anxiety and depression symptoms were measured. Interestingly, in genetically identical twin-pairs, the lack of leisure-time exercise did not increase anxiety or depression symptoms 126. However, this study took a very narrow approach at looking at exercise level, whereby physical activity, such as walking or cycling work, or vocational-related physical activity were not considered 570. Lastly, adolescent girls with an allele for high BDNF received no protective effects against depression and anxiety symptoms by avoiding physical inactivity, while those with the allele causing lower BDNF level were protected 329.

32.3.3.2 Animal

Exercise stress response has been looked at using rats selected for either high endurance (high-capacity runners; HCR) or low endurance (low-capacity runners; LCR) based on a run to volitional/behavioral exhaustion. Counter to the hypothesis, the HCR had more anxiety-like behavior on a maze test and higher levels of cortisol in response to a restraint test 546. The surprising result may be in part due to the fact that the HCR selection is based on avoiding the electrical shock and, thus, avoiding stress in addition to their volitional/behavioral endurance capacity.

32.4 Clinical significance

Physical inactivity causes up to one third of depression. Physical activity can primarily prevent 20% to 30% of depression.

33 Bone (Osteoporosis)

  1. Top of page
  2. Organization of Article
  3. Definitions
  4. Overview for Next Three Sections
  5. Summary of Daily Step Reductions from Antiquity
  6. History of Inactivity's Compromising Effects on Function and Health
  7. Cause Versus Treatment
  8. Mechanisms of Physical Inactivity and Activity Differ
  9. Gene-Exercise/Physical Inactivity Interactions
  10. Twin Studies: Modulation of Twin Phenotype by Physical Activity
  11. Variety of Training Types to Primarily Prevent Disease
  12. Diseasome of Physical Inactivity (35 Diseases/Conditions)
  13. Inactivity Accelerates Loss of Functional Capacities with Years of Life
  14. Prevention of Death by Primary Prevention of Physical Inactivity
  15. Metabolic Syndrome
  16. Presentation Strategy for Diseases Composing MS
  17. Obesity
  18. Inactivity Fosters Obese Comorbidities
  19. Insulin Sensitivity/Resistance
  20. Prediabetes
  21. Type 2 Diabetes
  22. Nonalcoholic Fatty Liver Disease
  23. Cardiovascular Diseases: All Types
  24. Presentation of Individual Cardiovascular Diseases
  25. Coronary Heart Disease
  26. Peripheral Arterial Disease
  27. Hypertension
  28. Stroke
  29. Congestive Heart Failure
  30. Known Mechanisms for CVD Risk Factors
  31. Deep Vein Thrombosis
  32. Cognitive Function
  33. Depression and Anxiety
  34. Bone (Osteoporosis)
  35. Osteoarthritis
  36. Balance
  37. Rheumatoid Arthritis
  38. Cancer
  39. Colon Cancer
  40. Breast Cancer
  41. Endometrial Cancer
  42. Activity Prevention of Female Reproductive Disorders
  43. Activity Prevention of Male Reproductive Disorders
  44. Pain
  45. Digestive Tract Diseases
  46. Chronic Respiratory Diseases
  47. Chronic Kidney Disease
  48. Clinical Significance of Physical Inactivity as One Cause of 35 Chronic Conditions
  49. Effectiveness of Drug Therapy for Simultaneous Primary Prevention of 35 Physical Inactivity Conditions
  50. Risk Factors Worsen Over 6 to 12 Months in RCTs
  51. Primary Prevention of Physical Inactivity: Childhood Developing Adult Disorders
  52. Public Policy
  53. Conclusion
  54. Acknowledgements
  55. References

33.1 Definition

Decrease in bone mass with decreased density and enlargement of bone spaces producing porosity and brittleness.

33.2 Etiology

Among males more than 50 years old, prevalence of osteoporosis and osteopenia was 6% and 47%, respectively; and in females more than 50 years of age, prevalence was 7% and 40%, respectively 201.

33.2.1 Etiology: Lack of gravity and physical inactivity

Four cosmonauts who spent up to 7 months on the Russian space station Mir lost approximately 1% to 1.6% of bone mineral density (BMD) mainly from the spine, femoral neck, trochanter, and pelvis 539. The space-flight data shows that loading bone (gravity) is a powerful stimulus to maintenance of bone mass. In spinal cord injury to one MZ twin, as compared to their noninjured MZ twin, bone mineral content and BMD were reduced 42% and 35% in the legs, respectively, and 50% and 29% in the pelvis, respectively 29. Nonweight-bearing athletes (bicycling) had lower bone mineral mass of whole body and spine than weight-bearing athletes in males 425, 426. The spinal cord injury and cycling data demonstrate that absence of gravitational loading is a powerful stimulus for loss of bone mass.

33.2.2 An actual cause: Lack of exercise

Bone is lost from the lumbar spine and femoral neck at the rate of approximately 1% per year in sedentary pre- and postmenopausal women (Fig. 13). Inactivity, that is, reduced gravitational loading and muscle contraction forces on the skeleton, might contribute to aging-associated bone loss as suggested by the studies described below.

thumbnail image

Figure 13. Peak value for bone mineral density (BMD) in third decade of life contributes to the age in later life at which threshold for osteoporosis is passed. The higher the peak value for BMD, the later age in life delays age at which BMD reaches the osteoporosis threshold, below which osteoporosis is diagnosed. The upper line reflects a population that had high bone-loading physical activities throughout lifespan with genes predisposing to high bone strength in contrast to the lower line reflecting low lifetime bone loading with genes predisposing to low bone strength. Adapted, with permission, from Rizzoli et al. 437 who modified original figure of Hernandez et al. 234.

Reproduced, with permission, from reference 437.

33.3 Primary prevention

Exercise-training programs prevent or reverse almost 1% of bone loss per year in the lumbar spine and femoral neck in both pre- and postmenopausal women, who were presumably sedentary, in a meta-analysis 571. Mixed loading exercise programs combining jogging with other low-impact loading activity and programs mixing impact activity with high-magnitude resistance exercise were effective in reducing postmenopausal bone loss at the hip and spine 328. In a first study, a 3-year program of combined low-volume, high-resistance strength training, and high-impact aerobics maintained BMD at the spine, hip, and calcaneus, but not at the forearm (which lost 3%), in early postmenopausal women 161. Importantly, the nontrained group BMD decreased 2% to 8% over the same 3-year period. These findings emphasize the clinical importance of avoiding inactivity in the early postmenopausal period and the specificity of the lack of impact on critical bones with high fracture rates in later life 161. In a second study, site-specific increases in bone density by RT happened in 50 to 70-year-old postmenopausal women and men who exercised approximately 3 to 4 days each week for 1 year 211. As in the first study, inactive “control” subjects lost bone mass.

Finally, it is important to emphasize the site specificity of exercise on bone. Only bones subject to loading will become stronger as adaptations are site specific. Further, not all weight-bearing exercise is equivalent when it comes to increasing bone mass/strength. For example, in comparisons, walking (which does relatively little) helps less than jogging, which helps less than jumping in maintaining bone mass.

33.4 Physiological mechanisms

Physical inactivity results in reduced mechanical, both gravitational and muscle contraction, forces which in turn induces catabolism (resorption) by promoting osteoclastogenesis with concurrent suppression of both bone formation and osteoblastogenesis. Dynamic exercise alters the balance between bone formation and resorption to favor anabolism through osteoblast recruitment and activity.

Mechanical loading of bone occurs in response to compressive forces from gravity during walking or running, or to in response to muscular forces at the bone attachments during contractions. Physical activity, alone, only increases strain on bone by approximately 0.1%. However, strains of 1% to 10% are needed to activate bone cells. The implication, then, is that a mechanism must therefore exist to amplify strains from physical activity (compressive impact forces from striking surfaces and tensile forces from contracting skeletal muscle at attachment sites to bone) to exceed the threshold needed to activate bone cells. Ozcivici et al. 393 conclude that mechanical targeting of the bone marrow stem-cell pool might, therefore, represent a novel, drug-free means of slowing the age-related decline of the musculoskeletal system.

33.5 Cellular mechanisms

Current thought for how a bone strain of approximately 0.1% can be amplified to a 1% to 10% has been suggested based upon 25 years of publications by Riddle and Donahue 436. Deformation of skeletal tissues induces pressurization of interstitial fluid, producing a positive pressure gradient from the matrix to the haversian cannels, allowing bone cells perceive changes in their mechanical environment (an amplification mechanism) 436. It is not completely settled whether the conversion of the physical force of fluid flow to a biochemical signal is by means of integrin/cytoskeletal transduction of forces or chemotransport ion channels, or both.

33.6 Clinical consequences

Physical inactivity is a primary cause of bone loss in weight-bearing bones. Physical activity results in both gravitational and muscle-contraction loading of the skeleton and, therefore, is primary prevention of osteoporosis.

34 Osteoarthritis

  1. Top of page
  2. Organization of Article
  3. Definitions
  4. Overview for Next Three Sections
  5. Summary of Daily Step Reductions from Antiquity
  6. History of Inactivity's Compromising Effects on Function and Health
  7. Cause Versus Treatment
  8. Mechanisms of Physical Inactivity and Activity Differ
  9. Gene-Exercise/Physical Inactivity Interactions
  10. Twin Studies: Modulation of Twin Phenotype by Physical Activity
  11. Variety of Training Types to Primarily Prevent Disease
  12. Diseasome of Physical Inactivity (35 Diseases/Conditions)
  13. Inactivity Accelerates Loss of Functional Capacities with Years of Life
  14. Prevention of Death by Primary Prevention of Physical Inactivity
  15. Metabolic Syndrome
  16. Presentation Strategy for Diseases Composing MS
  17. Obesity
  18. Inactivity Fosters Obese Comorbidities
  19. Insulin Sensitivity/Resistance
  20. Prediabetes
  21. Type 2 Diabetes
  22. Nonalcoholic Fatty Liver Disease
  23. Cardiovascular Diseases: All Types
  24. Presentation of Individual Cardiovascular Diseases
  25. Coronary Heart Disease
  26. Peripheral Arterial Disease
  27. Hypertension
  28. Stroke
  29. Congestive Heart Failure
  30. Known Mechanisms for CVD Risk Factors
  31. Deep Vein Thrombosis
  32. Cognitive Function
  33. Depression and Anxiety
  34. Bone (Osteoporosis)
  35. Osteoarthritis
  36. Balance
  37. Rheumatoid Arthritis
  38. Cancer
  39. Colon Cancer
  40. Breast Cancer
  41. Endometrial Cancer
  42. Activity Prevention of Female Reproductive Disorders
  43. Activity Prevention of Male Reproductive Disorders
  44. Pain
  45. Digestive Tract Diseases
  46. Chronic Respiratory Diseases
  47. Chronic Kidney Disease
  48. Clinical Significance of Physical Inactivity as One Cause of 35 Chronic Conditions
  49. Effectiveness of Drug Therapy for Simultaneous Primary Prevention of 35 Physical Inactivity Conditions
  50. Risk Factors Worsen Over 6 to 12 Months in RCTs
  51. Primary Prevention of Physical Inactivity: Childhood Developing Adult Disorders
  52. Public Policy
  53. Conclusion
  54. Acknowledgements
  55. References

34.1 Definition

Osteoarthritis (OA) is defined as the degeneration of cartilage and its underlying bone within a joint.

34.2 Etiology

The type and duration of physical activity is a key factor determining whether exercise is beneficial to joint health or not. Buckwalter wrote:

Participation in sports that cause minimal joint impact and torsional loading by people with normal joints and neuromuscular function may cause osteophyte (bony projections that form along joints) formation, but it has minimal, if any, effect on the risk of osteoarthritis. In contrast, participation in sports that subject joints to high levels of impact and torsional loading increases the risk of injury-induced joint degeneration. People with abnormal joint anatomy or alignment, previous joint injury or surgery, osteoarthritis, joint instability, articular surface incongruity or dysplasia, disturbances of joint or muscle innervation, or inadequate muscle strength have increased risk of joint damage during participation in athletics 71.”

The NPAGCR 411 lists sports/activities associated with an increased prevalence of incident OA as being ballet/modern dance, orienteering, running, track and field, football (American and Australian rules), team sports (basketball, soccer, and ice hockey), boxing, weight lifting, wrestling, tennis, and handball. Confirming the specificity of sport/activity is a longitudinal study that followed 45 long-distance runners and 53 control subjects from age 58 in 1984 until 2002 with a series of knee radiographs to examine the progression of OA 93. In 2002, 20% of runners and 32% of controls had prevalent OA, with 2.2% and 9.4% being severe. The small size of this study prevented this difference from reaching statistical significance. The NPAGCR 411 concluded that no evidence presently exists to indicate that regular moderate to vigorous physical activity of 30 to 60 min for general health benefits increases the risk of developing OA in those without preexisting major joint injury.

34.3 Clinical significance

Primary prevention would be to avoid those sports predisposing to later life development of OA.

35 Balance

  1. Top of page
  2. Organization of Article
  3. Definitions
  4. Overview for Next Three Sections
  5. Summary of Daily Step Reductions from Antiquity
  6. History of Inactivity's Compromising Effects on Function and Health
  7. Cause Versus Treatment
  8. Mechanisms of Physical Inactivity and Activity Differ
  9. Gene-Exercise/Physical Inactivity Interactions
  10. Twin Studies: Modulation of Twin Phenotype by Physical Activity
  11. Variety of Training Types to Primarily Prevent Disease
  12. Diseasome of Physical Inactivity (35 Diseases/Conditions)
  13. Inactivity Accelerates Loss of Functional Capacities with Years of Life
  14. Prevention of Death by Primary Prevention of Physical Inactivity
  15. Metabolic Syndrome
  16. Presentation Strategy for Diseases Composing MS
  17. Obesity
  18. Inactivity Fosters Obese Comorbidities
  19. Insulin Sensitivity/Resistance
  20. Prediabetes
  21. Type 2 Diabetes
  22. Nonalcoholic Fatty Liver Disease
  23. Cardiovascular Diseases: All Types
  24. Presentation of Individual Cardiovascular Diseases
  25. Coronary Heart Disease
  26. Peripheral Arterial Disease
  27. Hypertension
  28. Stroke
  29. Congestive Heart Failure
  30. Known Mechanisms for CVD Risk Factors
  31. Deep Vein Thrombosis
  32. Cognitive Function
  33. Depression and Anxiety
  34. Bone (Osteoporosis)
  35. Osteoarthritis
  36. Balance
  37. Rheumatoid Arthritis
  38. Cancer
  39. Colon Cancer
  40. Breast Cancer
  41. Endometrial Cancer
  42. Activity Prevention of Female Reproductive Disorders
  43. Activity Prevention of Male Reproductive Disorders
  44. Pain
  45. Digestive Tract Diseases
  46. Chronic Respiratory Diseases
  47. Chronic Kidney Disease
  48. Clinical Significance of Physical Inactivity as One Cause of 35 Chronic Conditions
  49. Effectiveness of Drug Therapy for Simultaneous Primary Prevention of 35 Physical Inactivity Conditions
  50. Risk Factors Worsen Over 6 to 12 Months in RCTs
  51. Primary Prevention of Physical Inactivity: Childhood Developing Adult Disorders
  52. Public Policy
  53. Conclusion
  54. Acknowledgements
  55. References

Balance is defined as the ability to maintain the center of gravity for the body within the base of support that produces minimal postural sway. Its etiology can be related to lack of usage of nervous system controlling skeletal muscle movement against gravity. For example, living in space for as little as 9 days accelerates problems of equilibrium on standing, walking, and coordination on return to Earth (caused by inappropriate neurovestibular responses) 539. With eyes closed on this platform, astronauts complain of having no sensation of falling. Similar balance dysfunctions occur with aging. It is likely that improper balance upon return to Earth from space flight and with aging have a common denominator of insufficient exercise against gravity. Lack of appropriate balance occurs in later life. The NPAGCR 411 concluded that the strong evidence exists in old Americans that the risk of falls is reduced from physical activity programs that emphasize both balance training and muscle-strengthening activity with some aerobic activity, especially walking. The NPAGCR 411 further indicates that no evidence indicates that planned physical activity reduces falls in adults and older adults who are not at risk for falls. The clinical significance for primary prevention requires exercises that retain normal balance to reduce falls in individuals at risk for falls 124.

35.1 Bone fracture/falls

Bone fracture is defined as a break, rupture, or crack in bone or cartilage. Physical inactivity, specifically lack of loading bones against gravity, will cause loss in bone density, which increases the risk of bone fracture. Physical inactivity is directly associated with fracture risk, particularly for fractures of the proximal femur (i.e., increased physical inactivity increases fracture risk), according to NPAGCR 411. Based on epidemiologic studies that evaluated present dose-response associations, the minimal levels of physical activity that were significantly associated with reduced fracture risk were at least 9 to 14.9 MET-h/week of physical activity. The METs translate to more than 4 h/week of walking (types of exercise that mechanically load the proximal femur as opposed to cycling 425 or other activities that do not load the femur). Primary prevention with exercises that load bones can reduce falls in those with balance irregularities, fall-related fractures, and several risk factors for falls in individuals with low bone density 124.

36 Rheumatoid Arthritis

  1. Top of page
  2. Organization of Article
  3. Definitions
  4. Overview for Next Three Sections
  5. Summary of Daily Step Reductions from Antiquity
  6. History of Inactivity's Compromising Effects on Function and Health
  7. Cause Versus Treatment
  8. Mechanisms of Physical Inactivity and Activity Differ
  9. Gene-Exercise/Physical Inactivity Interactions
  10. Twin Studies: Modulation of Twin Phenotype by Physical Activity
  11. Variety of Training Types to Primarily Prevent Disease
  12. Diseasome of Physical Inactivity (35 Diseases/Conditions)
  13. Inactivity Accelerates Loss of Functional Capacities with Years of Life
  14. Prevention of Death by Primary Prevention of Physical Inactivity
  15. Metabolic Syndrome
  16. Presentation Strategy for Diseases Composing MS
  17. Obesity
  18. Inactivity Fosters Obese Comorbidities
  19. Insulin Sensitivity/Resistance
  20. Prediabetes
  21. Type 2 Diabetes
  22. Nonalcoholic Fatty Liver Disease
  23. Cardiovascular Diseases: All Types
  24. Presentation of Individual Cardiovascular Diseases
  25. Coronary Heart Disease
  26. Peripheral Arterial Disease
  27. Hypertension
  28. Stroke
  29. Congestive Heart Failure
  30. Known Mechanisms for CVD Risk Factors
  31. Deep Vein Thrombosis
  32. Cognitive Function
  33. Depression and Anxiety
  34. Bone (Osteoporosis)
  35. Osteoarthritis
  36. Balance
  37. Rheumatoid Arthritis
  38. Cancer
  39. Colon Cancer
  40. Breast Cancer
  41. Endometrial Cancer
  42. Activity Prevention of Female Reproductive Disorders
  43. Activity Prevention of Male Reproductive Disorders
  44. Pain
  45. Digestive Tract Diseases
  46. Chronic Respiratory Diseases
  47. Chronic Kidney Disease
  48. Clinical Significance of Physical Inactivity as One Cause of 35 Chronic Conditions
  49. Effectiveness of Drug Therapy for Simultaneous Primary Prevention of 35 Physical Inactivity Conditions
  50. Risk Factors Worsen Over 6 to 12 Months in RCTs
  51. Primary Prevention of Physical Inactivity: Childhood Developing Adult Disorders
  52. Public Policy
  53. Conclusion
  54. Acknowledgements
  55. References

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by inflammation of the joints, frequently accompanied by marked deformities, and ordinarily associated with manifestations of a general, or systemic, affliction. While no preventive measures are currently known, physical activity is critical to not allowing RA to progress. Studies show no harmful effects of physical activity, and some even show a positive effect in the reduction of symptoms 73. High-intensity physical activity is better than low at preventing the worsening of symptoms. The mechanism by which physical activity has a beneficial effect on RA might be it's countering the global increase in inflammation that normally occurs during the progression of RA.

37 Cancer

  1. Top of page
  2. Organization of Article
  3. Definitions
  4. Overview for Next Three Sections
  5. Summary of Daily Step Reductions from Antiquity
  6. History of Inactivity's Compromising Effects on Function and Health
  7. Cause Versus Treatment
  8. Mechanisms of Physical Inactivity and Activity Differ
  9. Gene-Exercise/Physical Inactivity Interactions
  10. Twin Studies: Modulation of Twin Phenotype by Physical Activity
  11. Variety of Training Types to Primarily Prevent Disease
  12. Diseasome of Physical Inactivity (35 Diseases/Conditions)
  13. Inactivity Accelerates Loss of Functional Capacities with Years of Life
  14. Prevention of Death by Primary Prevention of Physical Inactivity
  15. Metabolic Syndrome
  16. Presentation Strategy for Diseases Composing MS
  17. Obesity
  18. Inactivity Fosters Obese Comorbidities
  19. Insulin Sensitivity/Resistance
  20. Prediabetes
  21. Type 2 Diabetes
  22. Nonalcoholic Fatty Liver Disease
  23. Cardiovascular Diseases: All Types
  24. Presentation of Individual Cardiovascular Diseases
  25. Coronary Heart Disease
  26. Peripheral Arterial Disease
  27. Hypertension
  28. Stroke
  29. Congestive Heart Failure
  30. Known Mechanisms for CVD Risk Factors
  31. Deep Vein Thrombosis
  32. Cognitive Function
  33. Depression and Anxiety
  34. Bone (Osteoporosis)
  35. Osteoarthritis
  36. Balance
  37. Rheumatoid Arthritis
  38. Cancer
  39. Colon Cancer
  40. Breast Cancer
  41. Endometrial Cancer
  42. Activity Prevention of Female Reproductive Disorders
  43. Activity Prevention of Male Reproductive Disorders
  44. Pain
  45. Digestive Tract Diseases
  46. Chronic Respiratory Diseases
  47. Chronic Kidney Disease
  48. Clinical Significance of Physical Inactivity as One Cause of 35 Chronic Conditions
  49. Effectiveness of Drug Therapy for Simultaneous Primary Prevention of 35 Physical Inactivity Conditions
  50. Risk Factors Worsen Over 6 to 12 Months in RCTs
  51. Primary Prevention of Physical Inactivity: Childhood Developing Adult Disorders
  52. Public Policy
  53. Conclusion
  54. Acknowledgements
  55. References

37.1 Definition

Cancer is defined as a malignant tumor of potentially unlimited growth that expands locally by invasion and systemically by metastasis.

37.2 Comments on cancer types

37.2.1 Majority of cancer prevalence has environmental component

Inherited genetic factors make a minor contribution to susceptibility to most types of neoplasms, implying that the environment has the principal role in causing sporadic cancer 318. A review on targets and pathways for cancer prevention exists 441.

37.2.2 Risks of only some cancers rise with physical inactivity

Physical inactivity increases the prevalence of some site-specific (colon, breast, and endometrial cancers), but, to date, not all cancer types. The specificity of cancer types enhanced by physical inactivity supports a notion that mechanisms of inactivity-induced cancers are specific to each site-specific cancer. Stated in an opposite manner, some cancer types are not caused by physical inactivity.

Those cancers whose risk is enhanced by inactivity will be considered later.

38 Colon Cancer

  1. Top of page
  2. Organization of Article
  3. Definitions
  4. Overview for Next Three Sections
  5. Summary of Daily Step Reductions from Antiquity
  6. History of Inactivity's Compromising Effects on Function and Health
  7. Cause Versus Treatment
  8. Mechanisms of Physical Inactivity and Activity Differ
  9. Gene-Exercise/Physical Inactivity Interactions
  10. Twin Studies: Modulation of Twin Phenotype by Physical Activity
  11. Variety of Training Types to Primarily Prevent Disease
  12. Diseasome of Physical Inactivity (35 Diseases/Conditions)
  13. Inactivity Accelerates Loss of Functional Capacities with Years of Life
  14. Prevention of Death by Primary Prevention of Physical Inactivity
  15. Metabolic Syndrome
  16. Presentation Strategy for Diseases Composing MS
  17. Obesity
  18. Inactivity Fosters Obese Comorbidities
  19. Insulin Sensitivity/Resistance
  20. Prediabetes
  21. Type 2 Diabetes
  22. Nonalcoholic Fatty Liver Disease
  23. Cardiovascular Diseases: All Types
  24. Presentation of Individual Cardiovascular Diseases
  25. Coronary Heart Disease
  26. Peripheral Arterial Disease
  27. Hypertension
  28. Stroke
  29. Congestive Heart Failure
  30. Known Mechanisms for CVD Risk Factors
  31. Deep Vein Thrombosis
  32. Cognitive Function
  33. Depression and Anxiety
  34. Bone (Osteoporosis)
  35. Osteoarthritis
  36. Balance
  37. Rheumatoid Arthritis
  38. Cancer
  39. Colon Cancer
  40. Breast Cancer
  41. Endometrial Cancer
  42. Activity Prevention of Female Reproductive Disorders
  43. Activity Prevention of Male Reproductive Disorders
  44. Pain
  45. Digestive Tract Diseases
  46. Chronic Respiratory Diseases
  47. Chronic Kidney Disease
  48. Clinical Significance of Physical Inactivity as One Cause of 35 Chronic Conditions
  49. Effectiveness of Drug Therapy for Simultaneous Primary Prevention of 35 Physical Inactivity Conditions
  50. Risk Factors Worsen Over 6 to 12 Months in RCTs
  51. Primary Prevention of Physical Inactivity: Childhood Developing Adult Disorders
  52. Public Policy
  53. Conclusion
  54. Acknowledgements
  55. References

38.1 Cross-sectional and longitudinal studies

A literature review through March 1997 found 23 case-control (cross-sectional) studies and 17 cohort (longitudinal) studies. In both types of studies, those in the highest physical activity category had approximately 40% to 50% reduction in risk of colon cancer compared with the least active category 111. A decade later, the NPAGCR 411 concluded physical activity produced a medium reduction of 30% in colon cancer from 8 case-control and 12 cohort studies, respectively.

38.2 Randomized control trials

The NPAGCR 411 states that RCTs have demonstrated effects of physical activity interventions on cancer risk factors, which further support a role of physical activity in reducing risk for cancer.

38.3 Mechanisms

38.3.1 Human

Suggestions by others how physical inactivity might increase prevalence of colon cancer are: (i) lengthening the transit time of feces, thus prolonging exposure to fecal carcinogens 114; (ii) causing higher levels of blood insulin, thus producing insulin resistance, which is a risk factor for cancer 197, 206; (iii) causing higher levels of blood free IGF-I 197, exposing the rapidly turning over colon epithelium to higher levels of anabolic hormone that is associated with greater colon cancer incidence 197; (iv) preventing synthesis and release of exercise-derived, anti-inflammatory myokines, thus removing their systemic effect 62; and/or (v) producing positive energy expenditure, increasing body fat 9.

38.3.2 Animal

ApcMin/+ mice have a nonsense mutation at codon 850 in the adenomatous polyposis coli (Apc) gene that predisposes them to both small and large intestinal adenomas, thus these mice have been used as a model of colon cancer 358. Colbert et al. reported two exercise studies using ApcMin/+ male mice. In their first study, 3 weeks of voluntary running followed by 5 weeks of treadmill running did not alter polyp development or serum IGF-I 106. In their second study of ApcMin/+ mice, 10 weeks of voluntary running decreased polyp number and increased serum IGF-I in male ApcMin/+, with IGF-I not being related to polyp number 107. Carson and coauthors observed that treadmill exercise reduced polyp number and size in male, but not female ApcMin/+ mice, while voluntary wheel running did not elicit a change in polyp number or size 336. Carson and coauthors reported that treadmill training caused intestinal polyps of ApcMin/+ mice to have 35%, 73%, and 43% decreases in macrophages, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL)-positive cells (index of apoptosis), and Bax protein 43% (proapoptotic protein), respectively 21. β-catenin phosphorylation was elevated 3.3-fold in polyps from these exercised mice. Ju et al. 261 found that colon tumorigenesis was approximately 40% greater in sedentary than voluntary running mice ApcMin/+ mice. The sedentary mice had higher IGF-1/IGFBP-3 ratios and aberrant β-catenin signaling, as compared to the voluntarily running mice 261.

38.4 Clinical significance

The lowest activity group has approximately 40% increased prevalence of colon cancer compared to the highest activity group. Physical activity is a primary preventer of colon cancer.

39 Breast Cancer

  1. Top of page
  2. Organization of Article
  3. Definitions
  4. Overview for Next Three Sections
  5. Summary of Daily Step Reductions from Antiquity
  6. History of Inactivity's Compromising Effects on Function and Health
  7. Cause Versus Treatment
  8. Mechanisms of Physical Inactivity and Activity Differ
  9. Gene-Exercise/Physical Inactivity Interactions
  10. Twin Studies: Modulation of Twin Phenotype by Physical Activity
  11. Variety of Training Types to Primarily Prevent Disease
  12. Diseasome of Physical Inactivity (35 Diseases/Conditions)
  13. Inactivity Accelerates Loss of Functional Capacities with Years of Life
  14. Prevention of Death by Primary Prevention of Physical Inactivity
  15. Metabolic Syndrome
  16. Presentation Strategy for Diseases Composing MS
  17. Obesity
  18. Inactivity Fosters Obese Comorbidities
  19. Insulin Sensitivity/Resistance
  20. Prediabetes
  21. Type 2 Diabetes
  22. Nonalcoholic Fatty Liver Disease
  23. Cardiovascular Diseases: All Types
  24. Presentation of Individual Cardiovascular Diseases
  25. Coronary Heart Disease
  26. Peripheral Arterial Disease
  27. Hypertension
  28. Stroke
  29. Congestive Heart Failure
  30. Known Mechanisms for CVD Risk Factors
  31. Deep Vein Thrombosis
  32. Cognitive Function
  33. Depression and Anxiety
  34. Bone (Osteoporosis)
  35. Osteoarthritis
  36. Balance
  37. Rheumatoid Arthritis
  38. Cancer
  39. Colon Cancer
  40. Breast Cancer
  41. Endometrial Cancer
  42. Activity Prevention of Female Reproductive Disorders
  43. Activity Prevention of Male Reproductive Disorders
  44. Pain
  45. Digestive Tract Diseases
  46. Chronic Respiratory Diseases
  47. Chronic Kidney Disease
  48. Clinical Significance of Physical Inactivity as One Cause of 35 Chronic Conditions
  49. Effectiveness of Drug Therapy for Simultaneous Primary Prevention of 35 Physical Inactivity Conditions
  50. Risk Factors Worsen Over 6 to 12 Months in RCTs
  51. Primary Prevention of Physical Inactivity: Childhood Developing Adult Disorders
  52. Public Policy
  53. Conclusion
  54. Acknowledgements
  55. References

39.1 Cross-sectional and longitudinal studies

The NPAGCR 411 concludes from 63 published studies that physical activity was associated with a medium reduction of 20% across all studies. However, the NPAGCR reports the range of reductions in breast cancer for all population-based case-control studies to be 20% to 70% and for cohort studies to be 20% to 80%.

The effect of physical activity on breast cancer reduction differs between pre- and postmenopausal conditions. A 2007 systemic review of 19 cohort and 29 case-control studies found a strong evidence for risk reductions ranging from 20% to 80% by physical activity for postmenopausal breast cancer 346. However, much weaker evidence is available for physical activities reduction on risk of premenopausal breast cancer, so no effect existed. Combining pre- and postmenopausal breast cancer resulted in a 15% to 20% decreased risk by physical activity. A trend analysis indicated a approximately 6% decrease in breast cancer risk for each additional hour of physical activity per week assuming that the level of activity would be sustained.

39.2 Mechanisms

Neilson 372 suggests that physical inactivity might increase breast cancer prevalence by any or the following: higher than normal BMI, androgens, estrogens, lifetime exposure to estrogen, leptin, insulin, insulin resistance, tumor necrosis factor-alpha (TNF-α), IL-6, CRP, and inflammation. Lower levels of steroid hormone binding protein by physical inactivity have been suggested to increase breast cancer risk. The mechanisms by which long-term physical activity lowers postmenopausal breast cancer risk, however, remain unclear 372.

Thompson et al.'s comprehensive review provides extensive literature to support three hypotheses by which physical inactivity could enhance breast cancer's prevalence 508. Hypothesis 1 proposes that inactivity-induced changes in circulating growth factors and hormones activate the mTOR-signaling network to increase proliferation and decrease apoptosis in breast cells while stimulating new blood vessel formation. Hypothesis 2 states that inactivity increases breast cells responsiveness to physiological stresses, potentially through FoxO, Sirtuin, and/or adipokine/myokine signaling. Hypothesis 3 says that inactivity increases glucose and glutamine availability in mammary carcinomas, thereby attenuating breast cell apoptosis and, thus, increasing the accumulation of breast tumor masses.

39.3 Clinical significance

The lowest activity group has approximately 25% increased prevalence of breast cancer compared to the highest activity group. Physical activity is a primary preventer of breast cancer.

40 Endometrial Cancer

  1. Top of page
  2. Organization of Article
  3. Definitions
  4. Overview for Next Three Sections
  5. Summary of Daily Step Reductions from Antiquity
  6. History of Inactivity's Compromising Effects on Function and Health
  7. Cause Versus Treatment
  8. Mechanisms of Physical Inactivity and Activity Differ
  9. Gene-Exercise/Physical Inactivity Interactions
  10. Twin Studies: Modulation of Twin Phenotype by Physical Activity
  11. Variety of Training Types to Primarily Prevent Disease
  12. Diseasome of Physical Inactivity (35 Diseases/Conditions)
  13. Inactivity Accelerates Loss of Functional Capacities with Years of Life
  14. Prevention of Death by Primary Prevention of Physical Inactivity
  15. Metabolic Syndrome
  16. Presentation Strategy for Diseases Composing MS
  17. Obesity
  18. Inactivity Fosters Obese Comorbidities
  19. Insulin Sensitivity/Resistance
  20. Prediabetes
  21. Type 2 Diabetes
  22. Nonalcoholic Fatty Liver Disease
  23. Cardiovascular Diseases: All Types
  24. Presentation of Individual Cardiovascular Diseases
  25. Coronary Heart Disease
  26. Peripheral Arterial Disease
  27. Hypertension
  28. Stroke
  29. Congestive Heart Failure
  30. Known Mechanisms for CVD Risk Factors
  31. Deep Vein Thrombosis
  32. Cognitive Function
  33. Depression and Anxiety
  34. Bone (Osteoporosis)
  35. Osteoarthritis
  36. Balance
  37. Rheumatoid Arthritis
  38. Cancer
  39. Colon Cancer
  40. Breast Cancer
  41. Endometrial Cancer
  42. Activity Prevention of Female Reproductive Disorders
  43. Activity Prevention of Male Reproductive Disorders
  44. Pain
  45. Digestive Tract Diseases
  46. Chronic Respiratory Diseases
  47. Chronic Kidney Disease
  48. Clinical Significance of Physical Inactivity as One Cause of 35 Chronic Conditions
  49. Effectiveness of Drug Therapy for Simultaneous Primary Prevention of 35 Physical Inactivity Conditions
  50. Risk Factors Worsen Over 6 to 12 Months in RCTs
  51. Primary Prevention of Physical Inactivity: Childhood Developing Adult Disorders
  52. Public Policy
  53. Conclusion
  54. Acknowledgements
  55. References

The NPAGCR 411 found growing evidence to support reduced risk of endometrial cancers in physically active versus sedentary persons. A meta-analysis of prospective studies published through to December 2009 found that physical activity was clearly associated with a 30% lower risk of endometrial cancer 347.

41 Activity Prevention of Female Reproductive Disorders

  1. Top of page
  2. Organization of Article
  3. Definitions
  4. Overview for Next Three Sections
  5. Summary of Daily Step Reductions from Antiquity
  6. History of Inactivity's Compromising Effects on Function and Health
  7. Cause Versus Treatment
  8. Mechanisms of Physical Inactivity and Activity Differ
  9. Gene-Exercise/Physical Inactivity Interactions
  10. Twin Studies: Modulation of Twin Phenotype by Physical Activity
  11. Variety of Training Types to Primarily Prevent Disease
  12. Diseasome of Physical Inactivity (35 Diseases/Conditions)
  13. Inactivity Accelerates Loss of Functional Capacities with Years of Life
  14. Prevention of Death by Primary Prevention of Physical Inactivity
  15. Metabolic Syndrome
  16. Presentation Strategy for Diseases Composing MS
  17. Obesity
  18. Inactivity Fosters Obese Comorbidities
  19. Insulin Sensitivity/Resistance
  20. Prediabetes
  21. Type 2 Diabetes
  22. Nonalcoholic Fatty Liver Disease
  23. Cardiovascular Diseases: All Types
  24. Presentation of Individual Cardiovascular Diseases
  25. Coronary Heart Disease
  26. Peripheral Arterial Disease
  27. Hypertension
  28. Stroke
  29. Congestive Heart Failure
  30. Known Mechanisms for CVD Risk Factors
  31. Deep Vein Thrombosis
  32. Cognitive Function
  33. Depression and Anxiety
  34. Bone (Osteoporosis)
  35. Osteoarthritis
  36. Balance
  37. Rheumatoid Arthritis
  38. Cancer
  39. Colon Cancer
  40. Breast Cancer
  41. Endometrial Cancer
  42. Activity Prevention of Female Reproductive Disorders
  43. Activity Prevention of Male Reproductive Disorders
  44. Pain
  45. Digestive Tract Diseases
  46. Chronic Respiratory Diseases
  47. Chronic Kidney Disease
  48. Clinical Significance of Physical Inactivity as One Cause of 35 Chronic Conditions
  49. Effectiveness of Drug Therapy for Simultaneous Primary Prevention of 35 Physical Inactivity Conditions
  50. Risk Factors Worsen Over 6 to 12 Months in RCTs
  51. Primary Prevention of Physical Inactivity: Childhood Developing Adult Disorders
  52. Public Policy
  53. Conclusion
  54. Acknowledgements
  55. References

41.1 Pregnancy

Multiple methodological pitfalls exist in the studies published 195, so conclusions made about benefits of physical activity on female reproductive health remain for further testing. Nonetheless, the consensus is that exercise can serve as primary prevention during pregnancy 195, 338. Maternal outcomes to be briefly discussed are gestational diabetes mellitus (GDM), pre-eclampsia, and weight gain [summaries below are taken from an extensive review 195].

41.2 Gestational diabetes mellitus

41.2.1 Definition

Gestational diabetes mallitus (GDM) is defined as any degree of glucose intolerance with onset, or first recognition, during pregnancy. Women in the high-risk category not found to have GDM at initial screening should be retested between 24 and 28 weeks of gestation.

41.2.2 Etiology

Overall prevalence of gestational diabetes is 4% to 8%, depending on US locale 201. The American Diabetes Association has stated, “Women with clinical characteristics consistent with a high risk of GDM (marked obesity, personal history of GDM, glycosuria, or a strong family history of diabetes) should undergo glucose testing as soon as feasible” 10. Note the statement does not include physical inactivity as a risk factor.

41.2.3 Exercise outcomes

Gavard and Artal have a lengthy review 195. They conclude that the balance of evidence is that exercise is protective against GDM. The protective effect seems to be particularly strong for vigorous or intense exercise, particularly for women reporting physical activity both before and during pregnancy. Studied in their review mentioned no deleterious exercise effects. Obviously, exceptions may occur and obstetricians should be consulted.

41.2.4 Clinical significance

GDM occurs during pregnancy and having GDM increases the risk of T2D later in life in both mothers and their offspring carried during GMD. Physical inactivity would increase chances of GDM. Physical activity is primary prevention.

41.3 Preeclampsia

41.3.1 Definition

A condition developing in late pregnancy that is characterized by a sudden rise in blood pressure, excessive weight gain, generalized edema, proteinuria, severe headache, and visual disturbances and that may result in eclampsia if untreated.

41.3.2 Exercise outcomes

Gavard and Artal 195 concluded that the balance of evidence still supports that exercise is the primary prevention against preeclampsia, with the effects being particularly strong for vigorous or intense exercise. No deleterious effects of exercise on preeclampsia were found, but Gavard and Artal caution that purposes of the investigations cited by them may not have been to report deleterious effects 195.

41.3.3 Clinical outcomes

Physical activity seems to be helpful in preventing pre-eclampsia from the limited numbers of studies on the topic.

41.4 Excessive weight gain during pregnancy

Gavard and Artal 195 conclude that prospective clinical trials are needed to establish exercise's effectiveness for lowering risk of maternal and fetal comorbidities during pregnancies with excessive weight gain. Likewise, Shirazian and Raghavan 470 call for prospective interventional studies to demonstrate the benefits of weight limitation on pregnancy outcomes.

41.5 Polycystic ovarian syndrome

41.5.1 Definition

Accumulation of numerous cysts on the ovaries associated with high male hormone levels, chronic anovulation, and other metabolic disturbances. Classic symptoms include excess facial and body hair, acne, obesity, irregular menstrual cycles, and infertility.

41.5.2 Exercise outcomes

Limited information is available for the primary prevention of polycystic ovarian syndrome (PCOS) by physical activity. Exercise appears to provide secondary/tertiary prevention, so studies of primary prevention seem justified. Thomson et al.'s review on treatment and management of PCOS conclude, “…few well-controlled randomized studies have been conducted evaluating the benefits of exercise training. Future research with rigorous study designs is needed to determine specific exercise guidelines…” 509.

41.6 Female athlete triad (Triad)

41.6.1 Definition

A combination of disorders frequently found in female athletes that includes disordered eating, osteoporosis, and oligo- or amenorrhea.

The Triad is discussed in detail by an American College of Sports Medicine position stand 369. The position stand places emphasis on optimizing energy availability for primary prevention. The stand also states, “No pharmacological agent adequately restores bone loss or corrects metabolic abnormalities that impair health and performance in athletes with functional hypothalamic amenorrhea” 369. Eating disorders warrant psychotherapy.

41.7 Dysmenorrhea

41.7.1 Definition

Dysmenorrhea is defined as painful cramps during menstruation.

41.7.2 Exercise outcomes

Physical exercise has been suggested as a nonmedical approach to manage these symptoms, but Cochrane review 66 cautions their conclusion is limited to a single RCT with a small sample size of limited quality. Primary prevention by physical activity may be plausible but is not sufficiently proven.

42 Activity Prevention of Male Reproductive Disorders

  1. Top of page
  2. Organization of Article
  3. Definitions
  4. Overview for Next Three Sections
  5. Summary of Daily Step Reductions from Antiquity
  6. History of Inactivity's Compromising Effects on Function and Health
  7. Cause Versus Treatment
  8. Mechanisms of Physical Inactivity and Activity Differ
  9. Gene-Exercise/Physical Inactivity Interactions
  10. Twin Studies: Modulation of Twin Phenotype by Physical Activity
  11. Variety of Training Types to Primarily Prevent Disease
  12. Diseasome of Physical Inactivity (35 Diseases/Conditions)
  13. Inactivity Accelerates Loss of Functional Capacities with Years of Life
  14. Prevention of Death by Primary Prevention of Physical Inactivity
  15. Metabolic Syndrome
  16. Presentation Strategy for Diseases Composing MS
  17. Obesity
  18. Inactivity Fosters Obese Comorbidities
  19. Insulin Sensitivity/Resistance
  20. Prediabetes
  21. Type 2 Diabetes
  22. Nonalcoholic Fatty Liver Disease
  23. Cardiovascular Diseases: All Types
  24. Presentation of Individual Cardiovascular Diseases
  25. Coronary Heart Disease
  26. Peripheral Arterial Disease
  27. Hypertension
  28. Stroke
  29. Congestive Heart Failure
  30. Known Mechanisms for CVD Risk Factors
  31. Deep Vein Thrombosis
  32. Cognitive Function
  33. Depression and Anxiety
  34. Bone (Osteoporosis)
  35. Osteoarthritis
  36. Balance
  37. Rheumatoid Arthritis
  38. Cancer
  39. Colon Cancer
  40. Breast Cancer
  41. Endometrial Cancer
  42. Activity Prevention of Female Reproductive Disorders
  43. Activity Prevention of Male Reproductive Disorders
  44. Pain
  45. Digestive Tract Diseases
  46. Chronic Respiratory Diseases
  47. Chronic Kidney Disease
  48. Clinical Significance of Physical Inactivity as One Cause of 35 Chronic Conditions
  49. Effectiveness of Drug Therapy for Simultaneous Primary Prevention of 35 Physical Inactivity Conditions
  50. Risk Factors Worsen Over 6 to 12 Months in RCTs
  51. Primary Prevention of Physical Inactivity: Childhood Developing Adult Disorders
  52. Public Policy
  53. Conclusion
  54. Acknowledgements
  55. References

42.1 Erectile dysfunction

42.1.1 Definition

Impotence, or erectile dysfunction (ED), is defined by the as the inability for a male to maintain erection of the penis sufficient for sexual performance.

42.1.2 Etiology

It is estimated that ED affects 30 million males in the United States. ED prevalence increases steadily with age, from 6.5% in men aged 20 to 29 years to 77.5% in those 75 years and older 452. In addition to physical inactivity, other risk factors are age, CVD, T2D, high cholesterol, smoking, recreational drug use, and depression are all risk factors. Erections are established through a set of well-known evens whereby neural stimulation (of various types) results in a release of nitric oxide, increased cGMP, and ultimately vasodilation of the smooth muscle in the arteries supplying the penis, which expands penile volume by increased blood flow into the corpora cavernosa. This process is reversed by phosphodiesterase type 5 (PDE5) breaking down cGMP; thus, pharmaceutical treatments of ED inhibit PDE5 activity.

42.1.3 Cross-sectional evidence

Several large cross-sectional studies exist to suggest that physical inactivity is a cause of ED. In a cohort of over 31,000 men over the age of 50, one third of men had ED 19. Men engaged in at least 32.6 MET equivalent hours of exercise per week had a significantly lower relative risk (0.7) than those undergoing less than 2.7 MET activity hours per week, a similar reduction in risk as obesity increased risk 19. For instance, in the Boston Area Community Health (BACH) Survey of 2031 males aged 30 to 79 lifestyle contributed to 12.2% of the total subject with clinically validated ED 294. However, when all covariates were considered, lifestyle alone could only explain 0.9% of the ED. In a prospective study from the same population, those went from no physical activity to some physical activity had a similar relative risk (OR of 0.5) as those that maintained high levels of physical activity (OR of 0.3) 131.

42.1.4 Interventional evidence

Utilizing a randomized-single bind design 110 obese men with ED, as defined by a International Index of Erectile Function (IIEF) less than 21, were either placed into an intervention group with the goal of 10% weight loss by walking 4 hours a week and reducing caloric intake or a control group. After 2 years, using an intent-to-treat analysis, the intervention group spent 195 min/week doing physical activity and had a significant improvement in IIEF scores from 13.9 to 17, with no change in the control group. Furthermore, physical inactivity levels were independently associated with ED 169. In a follow-up study using twice as many subjects, this same group demonstrated that lifestyle intervention for 2 years reduced the prevalence of ED from 66% to 44% 168. Those within the lifestyle group that exercised more than 4 h/week were 1.9 times more likely to reverse ED than those in the lifestyle group that remained sedentary, correcting for changes in diet and other lifestyle habits. Using a higher intensity exercise of 75% to 80% Vo2max for 60 min, three times a week, previously sedentary, but otherwise healthy men, had significant improvements in subjective sexual experiences. The improved sexual experiences correlated with the improvement in fitness 556.

42.1.5 Potential mechanisms

Since the underlying pathology of physical inactivity-induced impotence is similar to that of physical inactivity-induced endothelial function, many of the mechanisms though which exercise can be preventable are likely similar. However, the penile vasculature does not exhibit increased blood flow during treadmill running by Yucatan pigs 360. A few potential mediators of this are secreted factors from skeletal muscle (myokines), adipose tissue (adipokines), liver (hepatokines), or other changes in circulating factors, such as the physical activity-induced increased in testosterone in young, healthy men, and adolescent boys 130, 325, an important regulator of vasculature health [reviewed in reference 343]. Nevertheless, considerable evidence now suggests that chronic exercise training produces beneficial endothelial adaptations in vasculatures not recruited/active during exercise bouts.

42.1.6 Clinical significance of primary prevention

Physical inactivity is one cause of ED. Physical activity can be a primary preventer of ED.

42.2 Prostate cancer

The overall effects of physical activity on primary prevention of prostate cancer (PCa) are unclear. The NPAGCR concluded no association exists between physical activity and PCa 411. On the other hand, the NPAGCR states a statistically significant trend toward decreasing PCa risk was observed with increasing physical activity in several studies. Tertiary prevention may exist as Kenfield et al. 270 provided evidence that physical activity was associated with lower mortality and PCa mortality in men previously diagnosed with PCa. Barnard et al. 23 noted that serum from subjects performing regular aerobic exercise led to reduced growth and increased apoptosis of lymph node cancer of the prostate tumor cells in vitro.

43 Pain

  1. Top of page
  2. Organization of Article
  3. Definitions
  4. Overview for Next Three Sections
  5. Summary of Daily Step Reductions from Antiquity
  6. History of Inactivity's Compromising Effects on Function and Health
  7. Cause Versus Treatment
  8. Mechanisms of Physical Inactivity and Activity Differ
  9. Gene-Exercise/Physical Inactivity Interactions
  10. Twin Studies: Modulation of Twin Phenotype by Physical Activity
  11. Variety of Training Types to Primarily Prevent Disease
  12. Diseasome of Physical Inactivity (35 Diseases/Conditions)
  13. Inactivity Accelerates Loss of Functional Capacities with Years of Life
  14. Prevention of Death by Primary Prevention of Physical Inactivity
  15. Metabolic Syndrome
  16. Presentation Strategy for Diseases Composing MS
  17. Obesity
  18. Inactivity Fosters Obese Comorbidities
  19. Insulin Sensitivity/Resistance
  20. Prediabetes
  21. Type 2 Diabetes
  22. Nonalcoholic Fatty Liver Disease
  23. Cardiovascular Diseases: All Types
  24. Presentation of Individual Cardiovascular Diseases
  25. Coronary Heart Disease
  26. Peripheral Arterial Disease
  27. Hypertension
  28. Stroke
  29. Congestive Heart Failure
  30. Known Mechanisms for CVD Risk Factors
  31. Deep Vein Thrombosis
  32. Cognitive Function
  33. Depression and Anxiety
  34. Bone (Osteoporosis)
  35. Osteoarthritis
  36. Balance
  37. Rheumatoid Arthritis
  38. Cancer
  39. Colon Cancer
  40. Breast Cancer
  41. Endometrial Cancer
  42. Activity Prevention of Female Reproductive Disorders
  43. Activity Prevention of Male Reproductive Disorders
  44. Pain
  45. Digestive Tract Diseases
  46. Chronic Respiratory Diseases
  47. Chronic Kidney Disease
  48. Clinical Significance of Physical Inactivity as One Cause of 35 Chronic Conditions
  49. Effectiveness of Drug Therapy for Simultaneous Primary Prevention of 35 Physical Inactivity Conditions
  50. Risk Factors Worsen Over 6 to 12 Months in RCTs
  51. Primary Prevention of Physical Inactivity: Childhood Developing Adult Disorders
  52. Public Policy
  53. Conclusion
  54. Acknowledgements
  55. References

43.1 Definition

A basic bodily sensation that is induced by a noxious stimulus, received by free nerve endings, and characterized by physical discomfort.

43.2 Occurrence of low-back pain

One-quarter of adults have at least 1 day of low-back pain (LBP) in a 3-month period and most adults suffer from LBP at some point during their lives 191. Well-trained individuals seem to exhibit higher pain tolerance to skeletal muscle biopsies and to skin suturing, but to our knowledge clinical trials testing the hypothesis are not available.

43.3 Clinical trials

Limited evidence exists according to a systemic review of 10 RCTs and 5 non-RCTs for the overall effectiveness of exercise to prevent LBP in humans 31.

43.4 Mechanisms

Moderate-intensity aerobic exercise reduced cutaneous and deep tissue hyperalgesia induced by acidic saline and stimulated neurotrophic factor-3 synthesis in gastrocnemius but not the soleus muscle 468. Sharma et al. 468 caution that their results are limited to animal models and cannot be generalized to chronic pain syndromes in humans.

43.5 Clinical significance

Exercise training has been long suggested to reduce pain, but not to be a cure to the source of the pain [see 468 for references], but sufficient publications to verify the claim do not exist. Bell and Burnett's review 31 concludes that future research is needed to clarify which exercises are effective and the dose-response relationships regarding exercise and low-back-pain outcomes.

44 Digestive Tract Diseases

  1. Top of page
  2. Organization of Article
  3. Definitions
  4. Overview for Next Three Sections
  5. Summary of Daily Step Reductions from Antiquity
  6. History of Inactivity's Compromising Effects on Function and Health
  7. Cause Versus Treatment
  8. Mechanisms of Physical Inactivity and Activity Differ
  9. Gene-Exercise/Physical Inactivity Interactions
  10. Twin Studies: Modulation of Twin Phenotype by Physical Activity
  11. Variety of Training Types to Primarily Prevent Disease
  12. Diseasome of Physical Inactivity (35 Diseases/Conditions)
  13. Inactivity Accelerates Loss of Functional Capacities with Years of Life
  14. Prevention of Death by Primary Prevention of Physical Inactivity
  15. Metabolic Syndrome
  16. Presentation Strategy for Diseases Composing MS
  17. Obesity
  18. Inactivity Fosters Obese Comorbidities
  19. Insulin Sensitivity/Resistance
  20. Prediabetes
  21. Type 2 Diabetes
  22. Nonalcoholic Fatty Liver Disease
  23. Cardiovascular Diseases: All Types
  24. Presentation of Individual Cardiovascular Diseases
  25. Coronary Heart Disease
  26. Peripheral Arterial Disease
  27. Hypertension
  28. Stroke
  29. Congestive Heart Failure
  30. Known Mechanisms for CVD Risk Factors
  31. Deep Vein Thrombosis
  32. Cognitive Function
  33. Depression and Anxiety
  34. Bone (Osteoporosis)
  35. Osteoarthritis
  36. Balance
  37. Rheumatoid Arthritis
  38. Cancer
  39. Colon Cancer
  40. Breast Cancer
  41. Endometrial Cancer
  42. Activity Prevention of Female Reproductive Disorders
  43. Activity Prevention of Male Reproductive Disorders
  44. Pain
  45. Digestive Tract Diseases
  46. Chronic Respiratory Diseases
  47. Chronic Kidney Disease
  48. Clinical Significance of Physical Inactivity as One Cause of 35 Chronic Conditions
  49. Effectiveness of Drug Therapy for Simultaneous Primary Prevention of 35 Physical Inactivity Conditions
  50. Risk Factors Worsen Over 6 to 12 Months in RCTs
  51. Primary Prevention of Physical Inactivity: Childhood Developing Adult Disorders
  52. Public Policy
  53. Conclusion
  54. Acknowledgements
  55. References

44.1 Definition

The digestive tract begins in the mouth, ends in the anus, and includes accessory organs of digestion. Scores of digestive tract clinical conditions exist 367. Inactivity increases digestive system disorders. Some (cancers, nonalcoholic liver disease, and diabetic pancreas) are considered in elsewhere in the article.

44.2 Diverticulitis

44.2.1 Definition

Diverticulitis is an inflammatory swelling of an abnormal pouch (diverticulum) in the intestinal wall, usually in the large intestine (colon).

44.2.2 Physical activity is a primary preventer

Physical activity lowered the risk of diverticulitis and diverticular bleeding during an 18 years of follow-up of 47,228 US males in the Health Professionals Study 491. Vigorous-intensity activity subjects largely explained the association, a conclusion verified by Williams 561.

44.3 Gallbladder disease

44.3.1 Definition

Gallbladder disease includes inflammation, infection, stones, or blockage (obstruction) of the gallbladder.

44.3.2 Physical activity is a primary preventer

Physical activity levels are inversely related to prevalence of gallbladder disease in an American Indian population 284.

44.3.3 Mechanism

Treadmill running promoted changes in hepatic gene expression that increased cholesterol uptake by the liver while simultaneously increasing the catabolism of cholesterol to bile acids, thus effectively reducing cholesterol saturation in the bile. Wilund et al. 565 suggest their results describe a potential mechanism by which exercise improves cholesterol clearance from the circulation while simultaneously inhibiting gallstone formation.

44.4 Clinical significance

Observational studies suggest that diverticulitis, constipation, and gallbladder disease can be caused by physical inactivity and primarily prevented by increased activity. Physical activity may reduce the risk of gastrointestinal hemorrhage and inflammatory bowel disease although this cannot be substantiated firmly 408.

45 Chronic Respiratory Diseases

  1. Top of page
  2. Organization of Article
  3. Definitions
  4. Overview for Next Three Sections
  5. Summary of Daily Step Reductions from Antiquity
  6. History of Inactivity's Compromising Effects on Function and Health
  7. Cause Versus Treatment
  8. Mechanisms of Physical Inactivity and Activity Differ
  9. Gene-Exercise/Physical Inactivity Interactions
  10. Twin Studies: Modulation of Twin Phenotype by Physical Activity
  11. Variety of Training Types to Primarily Prevent Disease
  12. Diseasome of Physical Inactivity (35 Diseases/Conditions)
  13. Inactivity Accelerates Loss of Functional Capacities with Years of Life
  14. Prevention of Death by Primary Prevention of Physical Inactivity
  15. Metabolic Syndrome
  16. Presentation Strategy for Diseases Composing MS
  17. Obesity
  18. Inactivity Fosters Obese Comorbidities
  19. Insulin Sensitivity/Resistance
  20. Prediabetes
  21. Type 2 Diabetes
  22. Nonalcoholic Fatty Liver Disease
  23. Cardiovascular Diseases: All Types
  24. Presentation of Individual Cardiovascular Diseases
  25. Coronary Heart Disease
  26. Peripheral Arterial Disease
  27. Hypertension
  28. Stroke
  29. Congestive Heart Failure
  30. Known Mechanisms for CVD Risk Factors
  31. Deep Vein Thrombosis
  32. Cognitive Function
  33. Depression and Anxiety
  34. Bone (Osteoporosis)
  35. Osteoarthritis
  36. Balance
  37. Rheumatoid Arthritis
  38. Cancer
  39. Colon Cancer
  40. Breast Cancer
  41. Endometrial Cancer
  42. Activity Prevention of Female Reproductive Disorders
  43. Activity Prevention of Male Reproductive Disorders
  44. Pain
  45. Digestive Tract Diseases
  46. Chronic Respiratory Diseases
  47. Chronic Kidney Disease
  48. Clinical Significance of Physical Inactivity as One Cause of 35 Chronic Conditions
  49. Effectiveness of Drug Therapy for Simultaneous Primary Prevention of 35 Physical Inactivity Conditions
  50. Risk Factors Worsen Over 6 to 12 Months in RCTs
  51. Primary Prevention of Physical Inactivity: Childhood Developing Adult Disorders
  52. Public Policy
  53. Conclusion
  54. Acknowledgements
  55. References

45.1 Definition

Chronic diseases of the airways and other structures of the lung constitute chronic respiratory diseases. Some of the most common are asthma, chronic obstructive pulmonary disease (COPD), respiratory allergies, sleep apnea, occupational lung diseases, and pulmonary hypertension.

45.2 Etiology

Causes of these respiratory diseases are varied and include behavioral (smoking), environmental (air pollution and occupational hazards), and suppression of the immune system.

45.3 Physical inactivity

There are no studies to our knowledge showing that physical inactivity is associated with an increase in most COPDs. With sleep apnea it is difficult to determine whether physical inactivity is a cause or a result of the sleep apnea resulting in a viscous cycle of less sleep coupled with less activity 548. With asthma, an interaction of an increased environmental pollution with physical activity may be the factor for more recent studies finding higher asthma in athletes. In two cross-sectional studies, asthma was more prevalent in swimmers (OR = 10), long distance runners (OR = 6), and power athletes (OR = 3-4), than in less active individuals 231, 232. However, in contrast, an older study of Finnish athletes that died between 1936 and 1985 showed that they were no more likely to have asthma and about 50% less likely to die of any pulmonary disease than nonathletes 290. Our suggestion is that increased environmental pollution interacting with physical inactivity, rather than physical activity per se, is a major cause for increased asthma rates in athletes. The conclusion is consistent with an increase in asthma in the general population as well in the last several decades.

The sum of data suggests that a “J-shaped” curve exists where physical inactivity and extreme physical activity increase the risk the greatest for acquiring upper respiratory tract infections (URTI). While some prospective studies suggest a greater risk for URTI after a competitive event 380, 381, with increasing amount of training 228, 407, and higher in faster finishers 486 others show no difference after an event 158 and lower URTI with 6 to 7 METs/d of any activity 330. A decreased prevalence of URTI existed in two intervention studies utilizing lower levels of physical activity [one involving elderly women 379 and the other mildly obese females 382] However, many of these studies contain methodological problems including, failure to report bouts of physical activity, UTRI are only reported never verified by virus analysis, higher medical awareness during high-intensity training, contact with other infections (large marathon), stress, nutrition, supplements, and all the studies are focused on exercise not physical inactivity.

45.4 Mechanisms

There are several excellent reviews that the reader is directed to on immunosuppression following high levels of physical activity 64, 198, 400. The changes in immune function include low levels of lymphocytes and lymphocyte function 300, impaired phagocytosis, impaired neutrophilic function with prolonged exercise 400, neutrophil degranulation 399, reduced monocyte function 301, reduced oxidative burst activity, and potentially lower mucosal immunoglobulin levels 200.

45.5 Clinical significance

While regular moderate exercise reduces susceptibility to infection compared to sedentary, prolonged bouts of strenuous exercise cause a temporary depression of various aspects of immune function (e.g., neutrophil respiratory burst, lymphocyte proliferation, and monocyte antigen presentation) for approximately 3-24 h, for example, after prolonged (>1.5 h), of moderate to high intensity (55%-75% maximum O2 uptake) without food intake 198, 199. Periods of intensified training (overreaching) lasting 1 week or more may result in longer lasting immune dysfunction 198, 199

46 Chronic Kidney Disease

  1. Top of page
  2. Organization of Article
  3. Definitions
  4. Overview for Next Three Sections
  5. Summary of Daily Step Reductions from Antiquity
  6. History of Inactivity's Compromising Effects on Function and Health
  7. Cause Versus Treatment
  8. Mechanisms of Physical Inactivity and Activity Differ
  9. Gene-Exercise/Physical Inactivity Interactions
  10. Twin Studies: Modulation of Twin Phenotype by Physical Activity
  11. Variety of Training Types to Primarily Prevent Disease
  12. Diseasome of Physical Inactivity (35 Diseases/Conditions)
  13. Inactivity Accelerates Loss of Functional Capacities with Years of Life
  14. Prevention of Death by Primary Prevention of Physical Inactivity
  15. Metabolic Syndrome
  16. Presentation Strategy for Diseases Composing MS
  17. Obesity
  18. Inactivity Fosters Obese Comorbidities
  19. Insulin Sensitivity/Resistance
  20. Prediabetes
  21. Type 2 Diabetes
  22. Nonalcoholic Fatty Liver Disease
  23. Cardiovascular Diseases: All Types
  24. Presentation of Individual Cardiovascular Diseases
  25. Coronary Heart Disease
  26. Peripheral Arterial Disease
  27. Hypertension
  28. Stroke
  29. Congestive Heart Failure
  30. Known Mechanisms for CVD Risk Factors
  31. Deep Vein Thrombosis
  32. Cognitive Function
  33. Depression and Anxiety
  34. Bone (Osteoporosis)
  35. Osteoarthritis
  36. Balance
  37. Rheumatoid Arthritis
  38. Cancer
  39. Colon Cancer
  40. Breast Cancer
  41. Endometrial Cancer
  42. Activity Prevention of Female Reproductive Disorders
  43. Activity Prevention of Male Reproductive Disorders
  44. Pain
  45. Digestive Tract Diseases
  46. Chronic Respiratory Diseases
  47. Chronic Kidney Disease
  48. Clinical Significance of Physical Inactivity as One Cause of 35 Chronic Conditions
  49. Effectiveness of Drug Therapy for Simultaneous Primary Prevention of 35 Physical Inactivity Conditions
  50. Risk Factors Worsen Over 6 to 12 Months in RCTs
  51. Primary Prevention of Physical Inactivity: Childhood Developing Adult Disorders
  52. Public Policy
  53. Conclusion
  54. Acknowledgements
  55. References

Chronic kidney diseases (CKDs) damage the kidneys so that they are no longer capable of adequately removing fluids and wastes from the body or of maintaining the proper level of certain kidney-regulated chemicals in the bloodstream. CKD is a secondary consequence of physical inactivity's increasing hypertension and T2D prevalence. Albumin to creatine ratio (ACR) is a marker of kidney function. The US DPP found no change in ACR despite reductions in diabetes development with lifestyle reduction of T2D 136. In contrast, the Australian Diabetes, Obesity, and Lifestyle Study found that increased television watching or low self-reported leisure-time physical activity were associated with increased OR of albuminuria and low-estimated glomerular filtration rate in 6000 subjects 324, 557. Physical inactivity was one of multiple covariants accounting for early decline in renal function in 1400 US diabetic blacks 286. Norwegians (n = 65,000) undergoing no or little physical activity were twice as likely to have a low-estimated glomerular filtration rate 214. In summary, physical inactivity contributes to the development of CKD.

47 Clinical Significance of Physical Inactivity as One Cause of 35 Chronic Conditions

  1. Top of page
  2. Organization of Article
  3. Definitions
  4. Overview for Next Three Sections
  5. Summary of Daily Step Reductions from Antiquity
  6. History of Inactivity's Compromising Effects on Function and Health
  7. Cause Versus Treatment
  8. Mechanisms of Physical Inactivity and Activity Differ
  9. Gene-Exercise/Physical Inactivity Interactions
  10. Twin Studies: Modulation of Twin Phenotype by Physical Activity
  11. Variety of Training Types to Primarily Prevent Disease
  12. Diseasome of Physical Inactivity (35 Diseases/Conditions)
  13. Inactivity Accelerates Loss of Functional Capacities with Years of Life
  14. Prevention of Death by Primary Prevention of Physical Inactivity
  15. Metabolic Syndrome
  16. Presentation Strategy for Diseases Composing MS
  17. Obesity
  18. Inactivity Fosters Obese Comorbidities
  19. Insulin Sensitivity/Resistance
  20. Prediabetes
  21. Type 2 Diabetes
  22. Nonalcoholic Fatty Liver Disease
  23. Cardiovascular Diseases: All Types
  24. Presentation of Individual Cardiovascular Diseases
  25. Coronary Heart Disease
  26. Peripheral Arterial Disease
  27. Hypertension
  28. Stroke
  29. Congestive Heart Failure
  30. Known Mechanisms for CVD Risk Factors
  31. Deep Vein Thrombosis
  32. Cognitive Function
  33. Depression and Anxiety
  34. Bone (Osteoporosis)
  35. Osteoarthritis
  36. Balance
  37. Rheumatoid Arthritis
  38. Cancer
  39. Colon Cancer
  40. Breast Cancer
  41. Endometrial Cancer
  42. Activity Prevention of Female Reproductive Disorders
  43. Activity Prevention of Male Reproductive Disorders
  44. Pain
  45. Digestive Tract Diseases
  46. Chronic Respiratory Diseases
  47. Chronic Kidney Disease
  48. Clinical Significance of Physical Inactivity as One Cause of 35 Chronic Conditions
  49. Effectiveness of Drug Therapy for Simultaneous Primary Prevention of 35 Physical Inactivity Conditions
  50. Risk Factors Worsen Over 6 to 12 Months in RCTs
  51. Primary Prevention of Physical Inactivity: Childhood Developing Adult Disorders
  52. Public Policy
  53. Conclusion
  54. Acknowledgements
  55. References

47.1 Volume of evidence

Much of the article has presented evidence to prove that physical inactivity is a primary, upstream event that causes substantial increases in risk factors for 30 chronic diseases/conditions (Table 11; Fig. 3). The volume of evidence in itself is overwhelming. The clinical significance of physical activity itself is underappreciated as specific disease risk factors, themselves are often the prime objective of research and clinical care, rather than emphasis being placed on one major cause (physical inactivity) that is upstream of these risk factors.

Table 11. Estimations of the Incubation Durations to Overt Clinical Conditions for Diseases/Conditions Caused by Physical Inactivity and of the Percentage Reductions in Diseases Primarily Prevented by Physical Activity (Where Sufficient Information Exists in Healthy Humans Aged 20-65 Years of Age)
Disease/conditionInactivity causes (longer-term most days of the week implies years or decades while short term is weeks to months)

Exercise primarily prevents/delays

* Just meet guidelines for moderate activity (30 min/day), not intent treat.

** Our speculated asymptote for maximum in dose response.

∼ Indicates our speculated percentage.

Premature deathLong-term increaseYes, 30% reduction
Vo2max (CRF)30-year acceleration in lossYes, ** aerobic activity delays 30 years
Sarcopenia24-year acceleration to reachYes, ** resistance activity delays 24 years
Metabolic syndromeLong-term increaseYes, * 20%-30%; ** 80%
ObesityLong-term increaseYes, * 20%-30%; ** ∼80%
Insulin resistanceIncrease in 2-3 daysYes, * ∼80%; ** ∼95%
PrediabetesIntermediate-term increaseYes, * ∼80%; ** ∼95%
Type 2 diabetes mellitusLong-term increaseYes, * ∼80%; ** ∼95% (< 60 years old)
Nonalcoholic fatty liver diseaseLong-term increaseYes, * ∼80%; ** ∼95%
Coronary heart diseaseLong-term increaseYes, * 20%; ** 50%
Peripheral artery diseaseLong-term increaseYes, * 20%; ** 50%
HypertensionLong-term increaseYes, 2.3-mmHg lower diastolic blood pressure in hypertension translates into an estimated 12% and 24% increased risks for CHD and stroke, respectively.
StrokeLong-term increaseYes, * 25%; ** 35%
Congestive heart failureLong-term increaseYes, ∼ should be major percentage
Endothelial dysfunctionIncrease in hoursYes, asymptote should approach 90%
Atherogenic dysfunctionLong-term increaseYes, ∼ should be major percentage
HemostasisShorter-term increaseYes, ∼ should be minor percentage
Deep vein thrombosisIncrease in hoursYes, close to 100%
DementiaLong-term increaseYes, * 35%
Depression and anxietyShorter-term increaseYes, * 20%-30% (depression); * 30% (anxiety)
OsteoporosisLong-term maintenanceYes, ∼ should be major percentage
BalanceShorter-term lossYes, ∼ should be major percentage
Bone fracture/fallsLong-term increase in oldYes, * 35%-60% (hip fractures); * 30% (falls)
Colon cancerLong-term increaseYes, * 40%
Breast cancerLong-term increaseYes, * 25%
Endometrial cancerLong-term increaseYes, * 30%
Gestational diabetesIncrease in weeksYes, ∼ occurrence strengthens with predisposing genes
PreeclampsiaIncrease in weeksYes, insufficient information
Erectile dysfunctionLong-term increaseYes, asymptote should approach 90%
DiverticulitisLong-term increaseYes, insufficient information
ConstipationIncrease in daysYes, asymptote should approach 100%
Gallbladder diseasesLong-term increaseYes, insufficient information

47.2 Levels of evidence

Levels of evidence-based medicine vary in strength among the 30 chronic conditions caused by physical inactivity. Pressure toward evidence-based medicine has come from public and private health insurance providers, which refuse coverage of practices lacking in systematic evidence of usefulness. Levels of evidence are ranked for policy decision-making for health care distribution. The highest level of evidence is that there is a systemic review of RCT trials (Level 1) 94. The lowest level is based on mechanisms. However, models of extreme physical inactivity are so dramatic in the magnitude of health detriment that Human Institutional Research Boards (IRB), for ethical reasons if side effects were to be muscle atrophy, for example, the IRB would consider the risk and then review what arrangements have been made to mitigate this risk. Our speculation is that IRBs would likely be hesitant, for ethical reasons, to approve RCTs lasting years if irreversible overt chronic disease were to occur because of physical inactivity. Therefore, RCTs to prove long-term physical inactivity causes a chronic disease are unlikely to occur.

In 2008, the DPP Research Group commented:

“Debate prevails about whether resources (human and financial) would be better spent on T2DM prevention or on its early detection and treatment. Early detection is feasible through use of the same simple tests used in prevention programs, and could be done much more economically than attempting to prevent diabetes at the population level. Allocation of resources to intensive management of patients with newly diagnosed diabetes could be preferable to prevention. A major drawback of this approach, however, is that many people will have already developed macrovascular disease (and, rarely, microvascular disease) before diagnosis. Nonetheless, no data from clinical trials that have specifically compared prevention with early detection and intensive treatment have yet been reported 116.”

Narayan et al. already predicted in 2003 that 50% of US births in 2000 would have diabetes in their lifetime 365. Seven years later, the CDC has made a similar statement that diabetes prevalence could increase to 33% of the population in 2050 in the worse case scenario 61. Boyle et al. 61 predict that focusing on high-risk subgroups of the population the widespread implementation of reasonably effective preventive interventions could considerably reduce, but not eliminate, future increases in diabetes prevalence. Nonetheless, physical activity as primary prevention remains largely not reimbursable and mostly absent from evidence-based medical discussions.

47.2.1 Clinical significance

The primary prevention of physical inactivity is underappreciated.

48 Effectiveness of Drug Therapy for Simultaneous Primary Prevention of 35 Physical Inactivity Conditions

  1. Top of page
  2. Organization of Article
  3. Definitions
  4. Overview for Next Three Sections
  5. Summary of Daily Step Reductions from Antiquity
  6. History of Inactivity's Compromising Effects on Function and Health
  7. Cause Versus Treatment
  8. Mechanisms of Physical Inactivity and Activity Differ
  9. Gene-Exercise/Physical Inactivity Interactions
  10. Twin Studies: Modulation of Twin Phenotype by Physical Activity
  11. Variety of Training Types to Primarily Prevent Disease
  12. Diseasome of Physical Inactivity (35 Diseases/Conditions)
  13. Inactivity Accelerates Loss of Functional Capacities with Years of Life
  14. Prevention of Death by Primary Prevention of Physical Inactivity
  15. Metabolic Syndrome
  16. Presentation Strategy for Diseases Composing MS
  17. Obesity
  18. Inactivity Fosters Obese Comorbidities
  19. Insulin Sensitivity/Resistance
  20. Prediabetes
  21. Type 2 Diabetes
  22. Nonalcoholic Fatty Liver Disease
  23. Cardiovascular Diseases: All Types
  24. Presentation of Individual Cardiovascular Diseases
  25. Coronary Heart Disease
  26. Peripheral Arterial Disease
  27. Hypertension
  28. Stroke
  29. Congestive Heart Failure
  30. Known Mechanisms for CVD Risk Factors
  31. Deep Vein Thrombosis
  32. Cognitive Function
  33. Depression and Anxiety
  34. Bone (Osteoporosis)
  35. Osteoarthritis
  36. Balance
  37. Rheumatoid Arthritis
  38. Cancer
  39. Colon Cancer
  40. Breast Cancer
  41. Endometrial Cancer
  42. Activity Prevention of Female Reproductive Disorders
  43. Activity Prevention of Male Reproductive Disorders
  44. Pain
  45. Digestive Tract Diseases
  46. Chronic Respiratory Diseases
  47. Chronic Kidney Disease
  48. Clinical Significance of Physical Inactivity as One Cause of 35 Chronic Conditions
  49. Effectiveness of Drug Therapy for Simultaneous Primary Prevention of 35 Physical Inactivity Conditions
  50. Risk Factors Worsen Over 6 to 12 Months in RCTs
  51. Primary Prevention of Physical Inactivity: Childhood Developing Adult Disorders
  52. Public Policy
  53. Conclusion
  54. Acknowledgements
  55. References

48.1 Inability to mimic adaptive health benefits of physical activity

The natural adaptations to exercise provide a higher therapeutic index (benefits/side effects) than any drug therapy could exceed (Fig. 3). The high therapeutic index of exercise is in part due to its systemic complexity. It requires the integration of almost every physiological system (brain, neural, vascular, liver, adipose, muscle, etc.) to accomplish several basic physiological tasks such as movement and energy utilization. Since physical activity results in the whole body disruption of homeostasis in multiple organ systems, a drug therapy alone cannot replicate the entire ensemble its effects, without actually increasing physical activity. The complexity of physical activity is highlighted by comparison to other traits such as obesity. For instance, Reed et al. 430 estimate that 31% (extrapolated to 6000 genes) of all viable knockout mice have altered body weights. Such physiological complexity has been difficult to pharmacologically address with no FDA approved obesity drugs since 1999. Since the relative contribution of BMI for CVD and CHD has been estimated to be 10% and 7%, respectively 348, more than obesity is responsible for these diseases, making an “exercise pill” even less likely than obesity pill. We have published scientific criteria that must be met to legitimately use the terms exercise pill and “exercise mimetic” 52.

48.2 Clinical significance

Drugs will not substitute for all health benefits from physical activity in individuals medically capable of exercise.

49 Risk Factors Worsen Over 6 to 12 Months in RCTs

  1. Top of page
  2. Organization of Article
  3. Definitions
  4. Overview for Next Three Sections
  5. Summary of Daily Step Reductions from Antiquity
  6. History of Inactivity's Compromising Effects on Function and Health
  7. Cause Versus Treatment
  8. Mechanisms of Physical Inactivity and Activity Differ
  9. Gene-Exercise/Physical Inactivity Interactions
  10. Twin Studies: Modulation of Twin Phenotype by Physical Activity
  11. Variety of Training Types to Primarily Prevent Disease
  12. Diseasome of Physical Inactivity (35 Diseases/Conditions)
  13. Inactivity Accelerates Loss of Functional Capacities with Years of Life
  14. Prevention of Death by Primary Prevention of Physical Inactivity
  15. Metabolic Syndrome
  16. Presentation Strategy for Diseases Composing MS
  17. Obesity
  18. Inactivity Fosters Obese Comorbidities
  19. Insulin Sensitivity/Resistance
  20. Prediabetes
  21. Type 2 Diabetes
  22. Nonalcoholic Fatty Liver Disease
  23. Cardiovascular Diseases: All Types
  24. Presentation of Individual Cardiovascular Diseases
  25. Coronary Heart Disease
  26. Peripheral Arterial Disease
  27. Hypertension
  28. Stroke
  29. Congestive Heart Failure
  30. Known Mechanisms for CVD Risk Factors
  31. Deep Vein Thrombosis
  32. Cognitive Function
  33. Depression and Anxiety
  34. Bone (Osteoporosis)
  35. Osteoarthritis
  36. Balance
  37. Rheumatoid Arthritis
  38. Cancer
  39. Colon Cancer
  40. Breast Cancer
  41. Endometrial Cancer
  42. Activity Prevention of Female Reproductive Disorders
  43. Activity Prevention of Male Reproductive Disorders
  44. Pain
  45. Digestive Tract Diseases
  46. Chronic Respiratory Diseases
  47. Chronic Kidney Disease
  48. Clinical Significance of Physical Inactivity as One Cause of 35 Chronic Conditions
  49. Effectiveness of Drug Therapy for Simultaneous Primary Prevention of 35 Physical Inactivity Conditions
  50. Risk Factors Worsen Over 6 to 12 Months in RCTs
  51. Primary Prevention of Physical Inactivity: Childhood Developing Adult Disorders
  52. Public Policy
  53. Conclusion
  54. Acknowledgements
  55. References

49.1 RCTs

The definition of chronic diseases contains the word “ongoing.” Slentz et al. 480 cite evidence to support the notion, “continued sedentary lifestyle in overweight or obese individuals—particularly those who already have some metabolic abnormalities–comes at a high metabolic cost, as numerous health-related variables worsen over relatively short time periods” 51, 123, 217, 256. Examples from their own studies are given. Twelve markers that increase the risk of chronic diseases became worse in the 6-month inactive “control group,” including increases in body weight, waist circumference, waist-to-hip ratio, VAT, total abdominal fat, fasting insulin, LDL particle number, small dense LDL and LDL-cholesterol; and decreases in insulin sensitivity, and fitness 35, 153, 245, 256, 283, 480.

Hunter et al. 250 have published similar decrements for inactive “control” groups. Aerobic- and resistance-exercise adherence for 1 year prevented regain of VAT in healthy, overweight, premenopausal women following a weight loss of 12 kg 250. Specifically, aerobic or resistance exercise adherers did not change in VAT mass (1.6% and 0%, respectively) (80 min/week), contrary to a 38% increased VAT in the nonexercise adherers. While aerobic and resistance exercise adherers still regained 3.1 and 3.9 kg of body weight, respectively, it was significantly less than the 6.2 kg regain in exercise nonadherers, which was similar to the 6.4 kg gained in the group that did not exercise 250. Thus, sedentary controls became less healthy by increasing risk factors for chronic diseases, compared to exercising groups in both the Slentz et al. 480 and the Hunter et al. 250 studies. Together the two studies illustrate contemporary inactive control groups have a progressive worsening for risk factors of chronic diseases that physical activity can be a primary prevention against. A similar theme was apparent for osteoporosis, presented earlier in this article, that is, bones in nonbone loading group lose mass and density over a period of months. Importantly, the previous studies fit the definition of “slow in its progress and of long continuance” for chronic diseases 550. The pathological events from sedentary lifestyle are slow in progress.

50 Primary Prevention of Physical Inactivity: Childhood Developing Adult Disorders

  1. Top of page
  2. Organization of Article
  3. Definitions
  4. Overview for Next Three Sections
  5. Summary of Daily Step Reductions from Antiquity
  6. History of Inactivity's Compromising Effects on Function and Health
  7. Cause Versus Treatment
  8. Mechanisms of Physical Inactivity and Activity Differ
  9. Gene-Exercise/Physical Inactivity Interactions
  10. Twin Studies: Modulation of Twin Phenotype by Physical Activity
  11. Variety of Training Types to Primarily Prevent Disease
  12. Diseasome of Physical Inactivity (35 Diseases/Conditions)
  13. Inactivity Accelerates Loss of Functional Capacities with Years of Life
  14. Prevention of Death by Primary Prevention of Physical Inactivity
  15. Metabolic Syndrome
  16. Presentation Strategy for Diseases Composing MS
  17. Obesity
  18. Inactivity Fosters Obese Comorbidities
  19. Insulin Sensitivity/Resistance
  20. Prediabetes
  21. Type 2 Diabetes
  22. Nonalcoholic Fatty Liver Disease
  23. Cardiovascular Diseases: All Types
  24. Presentation of Individual Cardiovascular Diseases
  25. Coronary Heart Disease
  26. Peripheral Arterial Disease
  27. Hypertension
  28. Stroke
  29. Congestive Heart Failure
  30. Known Mechanisms for CVD Risk Factors
  31. Deep Vein Thrombosis
  32. Cognitive Function
  33. Depression and Anxiety
  34. Bone (Osteoporosis)
  35. Osteoarthritis
  36. Balance
  37. Rheumatoid Arthritis
  38. Cancer
  39. Colon Cancer
  40. Breast Cancer
  41. Endometrial Cancer
  42. Activity Prevention of Female Reproductive Disorders
  43. Activity Prevention of Male Reproductive Disorders
  44. Pain
  45. Digestive Tract Diseases
  46. Chronic Respiratory Diseases
  47. Chronic Kidney Disease
  48. Clinical Significance of Physical Inactivity as One Cause of 35 Chronic Conditions
  49. Effectiveness of Drug Therapy for Simultaneous Primary Prevention of 35 Physical Inactivity Conditions
  50. Risk Factors Worsen Over 6 to 12 Months in RCTs
  51. Primary Prevention of Physical Inactivity: Childhood Developing Adult Disorders
  52. Public Policy
  53. Conclusion
  54. Acknowledgements
  55. References

50.1 Prevalence of physical inactivity in youth

Fifty eight percent and 92% of American children aged 6 to 11 and 12 to 19 years old, respectively, do not meet the recommended 60 min of daily physical activity 526. Seventy three percent to 91% of Canadian children do not accomplish sufficient daily step numbers 76. A study was performed to compare lifestyle of children reminiscent of 100 years ago versus modern children. Eleven-year-old accelerometer values were found the following progressive declines in physical activity in weekday minutes of activity per day: Old-Order-Amish (90 min) > Old-Order-Mennonite (69 min) > rural Saskatchewan (58 min) > urban Saskatchewan (49 min) 167. Tremblay et al. have commented, “Groups that preserve a traditional lifestyle, with significant incidental, lifestyle-embedded, physical activities, appear to achieve high levels of daily physical activity and fitness and resist obesity” 524.

50.2 Obesity in children and adolescents

Between the mid-1960s and mid-1980s, childhood and adolescent obesity ranged between 4% and 6% (Fig. 14). About 25 years later (mid-1980s-2008), obesity (> 95% BMI percentile for children in the 1960s) in children (6-11 years) had risen 5-fold from approximately 4% in 1963 to 1974 to 20% in 2007 to 2008, and in adolescents (12-19 years) rose 3-fold from approximately 5% to 6% in between 1966 and 1980 to 18% in 2007 and 2008 (Fig. 14) 385, 386. Even with a more liberal cutoff for overweight and obesity, 36% of children and 34% of adolescents, rather than 15% were above the 85th percentile of the 1960s 385. Higher BMI during childhood is associated with an increased risk of CHD in adulthood 20.

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Figure 14. Rise in childhood and adolescent obesity in United States From 1980s through 2007 to 2008 obesity in 2 to 5, 6 to 11, and 12 to 19-year-old US females increased 3- to 5-fold. [Tabular data is converted from graphic, with permission, from references 385, 386].

50.3 Fasting blood glucose

The number of youth with elevated fasting blood sugar increased 87% from 1999 to 2000 through 2005 to 2006 317. The children with high fasting blood glucose have 49% lower glucose deposition index 503. More importantly, children with elevated fasting blood glucose were 3.4 and 2.1 times more likely to develop prediabetes and diabetes, respectively, as adults 377.

50.4 Prediabetes in children and adolescents

The number of US adolescents with elevated fasting glucose reached approximately 2,769,000 in 1999 to 2002 147. Within this population, adolescents of Mexican Americans decent are overrepresented (15.3% of all Mexican American adolescents) relative to non-Hispanic whites (11.3%) and non-Hispanic black adolescents (7.4%).

50.5 Adult-onset diabetes in our adolescents

Once considered a disease of adults, T2D is becoming increasingly common among adolescents 375 with approximately 39,005 US adolescents having T2D in 1999 to 2002, and now almost as common as T1D in some pediatric populations 147. Children in whom T2D develops are at earlier risks for complications as adults from the disease, including retinopathy, neuropathy, and cardiovascular and renal disease that may require decades of treatment 187. Primary prevention of T2D is essential in children and adolescents 326.

The estimated lifetime risk of developing diabetes for children born in 2000 is 32.8% for males and 38.5% for females, about 10% to 15% higher than current prevalence 365. This risk is higher for Hispanics, at 45.4% for males and 52.5% for females. In addition to developing complications, adolescents diagnosed as having diabetes have large reductions in life expectancy. For example, Narayan et al. 365 estimated that if diagnosed with T2D at the age of 20 years, males and females would die 17 and 18 years before normal, with a reduction of 27 and 30 quality-life adjusted years.

50.6 Metabolic syndrome in adolescents

A major problem with identifying the metabolic syndrome in children and adolescents is that there are no established criteria in this population 314. According to Cook et al. 113, “In obese adolescents only, the prevalence rates were 44.2% using the definition of Cook/Ford, 26.2% using the adult criteria, 14.1% using the definition of Caprio, and 12.4% using the definition of Cruz” [as different modifications of adult criteria for the metabolic syndrome were applied, the specific criteria can be located in Table 1 of reference 113]. Children with BMI and waist circumference values greater than normal values are at increased risk for the adult metabolic syndrome 499. Morrison et al. 355 contend that evaluating 5- to 19-year-old children for metabolic syndrome and family history of diabetes could identify children at increased risk of adult metabolic syndrome and T2D, allowing prospective primary prevention of these outcomes.

50.7 Atherosclerosis

Atherosclerosis is a consequence of lifetime accumulation of vascular lesions and plaques. Expectedly, Gillman indicates that the extent of coronary lesions in adolescents is associated with risk factors including lipids, smoking, blood pressure, obesity, and hyperglycemia (we add inactivity as a risk factor). Reversibility of childhood metabolic syndrome is rare, thus leading to high risk of adulthood CVD 196, 547.

50.8 Nonalcoholic fatty liver disease in children

The prevalence of NAFLD among normal-weight children is 3% to 10%, rising up to 40% to 70% among obese children 32, 33.

50.9 Cognitive function

Children and adolescents who are physically inactive will develop less cognitive skills than more active cohorts, as discussed in Section “Cognitive Function.”

50.10 Peak lifetime value determines years to reach clinical disease

Increases in bone mineral mass, skeletal muscle mass, and CRF occur throughout childhood and adolescence peaking and have their greatest lifetime values in the third decade of life. Thereafter with aging, their respective values progressively decline to lower values, at some age reaching a threshold past which an overt clinical condition has an increased probability of existing (osteoporosis, sarcopenia, and endurance frailty).

50.10.1 Bone: Less weight-bearing activity by children/adolescents results in earlier osteoporosis

After the age of approximately 25 years, BMD is progressively lost. As some age, BMD passes a threshold of an overt clinical event (osteoporosis). For example, a 25-year-old individual with a BMD that is 90% of the mean peak BMD be osteoporotic approximately 30 years earlier than if they had a BMD 110% of the mean peak BMD (Fig. 13).

The positive effect of mechanical loading on bone growth is greatest pre- and early puberty in girls 25 and prepuberty in boys 146. Thus, less load-bearing activity by children during skeletal growth is associated with smaller bone mass than in load-bearing children 437, 462. For example, girls starting at ages 9 to 15 had substantially greater increases in bone mineral content at lumbar spine and femoral neck if they had the highest physical activity levels during the 7-year follow-up as compared with those having the lowest physical activity levels 423. Thus, Rizzoli et al. 437 assert that childhood and adolescence is a key determinant of bone health and future fracture risk during adulthood.

50.10.2 Skeletal muscle: Less weight-bearing activity by children/adolescents results in earlier sarcopenia

In an earlier section (Prevention of Death by Primary Prevention of Physical Inactivity), skeletal muscle power peaks about the third decade of life, and then declines thereafter (Fig. 6). However, physically inactive individuals reached skeletal muscle frailty 24 years younger in age than masters’ weight lifters.

50.10.3 CRF: Less endurance-type play in children/adolescents increases risk of earlier death at old age

Figure 4 in the earlier section (Sedentary lifestyle speeds secondary aging of Vo2max by 30 years), showed that Vo2max peaks at the third decade of life, and thereafter declines. However, physically inactive individuals passed below the threshold of aerobic frailty 30 years earlier in age than masters’ aerobically trained individuals.

50.11 Summary

Physical inactivity is a cause of chronic disease in children and adolescents. Documented health benefits by prevention of physical inactivity in children and adolescents 411, 493 include increased physical fitness (both CRF and muscular strength), reduced body fatness, favorable cardiovascular and metabolic disease risk profiles, enhanced bone health, and reduced symptoms of depression and anxiety.

51 Public Policy

  1. Top of page
  2. Organization of Article
  3. Definitions
  4. Overview for Next Three Sections
  5. Summary of Daily Step Reductions from Antiquity
  6. History of Inactivity's Compromising Effects on Function and Health
  7. Cause Versus Treatment
  8. Mechanisms of Physical Inactivity and Activity Differ
  9. Gene-Exercise/Physical Inactivity Interactions
  10. Twin Studies: Modulation of Twin Phenotype by Physical Activity
  11. Variety of Training Types to Primarily Prevent Disease
  12. Diseasome of Physical Inactivity (35 Diseases/Conditions)
  13. Inactivity Accelerates Loss of Functional Capacities with Years of Life
  14. Prevention of Death by Primary Prevention of Physical Inactivity
  15. Metabolic Syndrome
  16. Presentation Strategy for Diseases Composing MS
  17. Obesity
  18. Inactivity Fosters Obese Comorbidities
  19. Insulin Sensitivity/Resistance
  20. Prediabetes
  21. Type 2 Diabetes
  22. Nonalcoholic Fatty Liver Disease
  23. Cardiovascular Diseases: All Types
  24. Presentation of Individual Cardiovascular Diseases
  25. Coronary Heart Disease
  26. Peripheral Arterial Disease
  27. Hypertension
  28. Stroke
  29. Congestive Heart Failure
  30. Known Mechanisms for CVD Risk Factors
  31. Deep Vein Thrombosis
  32. Cognitive Function
  33. Depression and Anxiety
  34. Bone (Osteoporosis)
  35. Osteoarthritis
  36. Balance
  37. Rheumatoid Arthritis
  38. Cancer
  39. Colon Cancer
  40. Breast Cancer
  41. Endometrial Cancer
  42. Activity Prevention of Female Reproductive Disorders
  43. Activity Prevention of Male Reproductive Disorders
  44. Pain
  45. Digestive Tract Diseases
  46. Chronic Respiratory Diseases
  47. Chronic Kidney Disease
  48. Clinical Significance of Physical Inactivity as One Cause of 35 Chronic Conditions
  49. Effectiveness of Drug Therapy for Simultaneous Primary Prevention of 35 Physical Inactivity Conditions
  50. Risk Factors Worsen Over 6 to 12 Months in RCTs
  51. Primary Prevention of Physical Inactivity: Childhood Developing Adult Disorders
  52. Public Policy
  53. Conclusion
  54. Acknowledgements
  55. References

51.1 Underappreciated cost

The NPAGCR 411 indicates that physical activity diminishes mortality by 30% in the United States. Stated alternatively, physical inactivity increases mortality by 30%, or by 720,000 annual deaths (one death every 44 s). Our estimations are that US health care costs of inactivity will range from $2.2 to $3.8 trillion in the first decade of the 21st century, or $700 yearly ($7000 for the next decade) from each US resident. Our estimate of physical inactivity's cost is in line with (i) the Society of Actuaries estimate that overweight and obesity cost the US $270 billion/year (cost includes increased need for medical care, and loss of economic productivity resulting from excess mortality and disability) 484 and (ii) the estimated nationwide cost of for physical inactivity and obesity of $507 billion with projected costs exceeding $708 billion in 2008 98. We estimate that if every US individual had 30 min of moderate physical activity per day obesity, annual US health costs would be reduced by approximately 4% ($100 billion of $2.4 trillion), and additionally we speculate that if all US individuals would approach the physical activity levels of US Amish, obesity would be reduced by approximately 8% ($200 billion of $2.4 trillion). Further, physical activity reduces prevalence of many conditions that are not obesity comorbidities, so we contend our estimates of physical inactivity are conservative and underestimates.

51.2 Role of exercise scientists in public policy

According to Kersh and Morone, “Public health crusades are typically built on a scientific base. In any event, medical knowledge in itself is rarely enough to stimulate a political response. Rather, the key to its impact lies in the policy entrepreneurs who spread the medical findings” 271. Scientists enable the enablers. Exercise and chronic diseases are complex polygenic conditions. The scientific and technical expertise to appreciate the complexity of exercise/inactivity and chronic diseases is limited within the scientific community. Thus, policy entrepreneurs must be careful in their selection of scientists to enable their public policy. The information in this article was presented both to enable both scientists and policy entrepreneurs to reduce physical inactivity-caused diseases.

52 Conclusion

  1. Top of page
  2. Organization of Article
  3. Definitions
  4. Overview for Next Three Sections
  5. Summary of Daily Step Reductions from Antiquity
  6. History of Inactivity's Compromising Effects on Function and Health
  7. Cause Versus Treatment
  8. Mechanisms of Physical Inactivity and Activity Differ
  9. Gene-Exercise/Physical Inactivity Interactions
  10. Twin Studies: Modulation of Twin Phenotype by Physical Activity
  11. Variety of Training Types to Primarily Prevent Disease
  12. Diseasome of Physical Inactivity (35 Diseases/Conditions)
  13. Inactivity Accelerates Loss of Functional Capacities with Years of Life
  14. Prevention of Death by Primary Prevention of Physical Inactivity
  15. Metabolic Syndrome
  16. Presentation Strategy for Diseases Composing MS
  17. Obesity
  18. Inactivity Fosters Obese Comorbidities
  19. Insulin Sensitivity/Resistance
  20. Prediabetes
  21. Type 2 Diabetes
  22. Nonalcoholic Fatty Liver Disease
  23. Cardiovascular Diseases: All Types
  24. Presentation of Individual Cardiovascular Diseases
  25. Coronary Heart Disease
  26. Peripheral Arterial Disease
  27. Hypertension
  28. Stroke
  29. Congestive Heart Failure
  30. Known Mechanisms for CVD Risk Factors
  31. Deep Vein Thrombosis
  32. Cognitive Function
  33. Depression and Anxiety
  34. Bone (Osteoporosis)
  35. Osteoarthritis
  36. Balance
  37. Rheumatoid Arthritis
  38. Cancer
  39. Colon Cancer
  40. Breast Cancer
  41. Endometrial Cancer
  42. Activity Prevention of Female Reproductive Disorders
  43. Activity Prevention of Male Reproductive Disorders
  44. Pain
  45. Digestive Tract Diseases
  46. Chronic Respiratory Diseases
  47. Chronic Kidney Disease
  48. Clinical Significance of Physical Inactivity as One Cause of 35 Chronic Conditions
  49. Effectiveness of Drug Therapy for Simultaneous Primary Prevention of 35 Physical Inactivity Conditions
  50. Risk Factors Worsen Over 6 to 12 Months in RCTs
  51. Primary Prevention of Physical Inactivity: Childhood Developing Adult Disorders
  52. Public Policy
  53. Conclusion
  54. Acknowledgements
  55. References

Physical activity, food, and reproduction are some of the minimal requirements for life. They evolved not as choices, but as requirements for individual and species survival. Modern humans have been able to engineer most physical activity out of daily life. Humans now have a choice not to be physically active. Conclusive and overwhelming scientific evidence, largely ignored and prioritized as low, exists for physical inactivity as a primary and actual cause of most chronic diseases. Thus, longer-term health was also engineered out with the successful removal of physical activity as a necessity for immediate survival. The comprehensive evidence herein clearly establishes that lack of physical activity affects almost every cell, organ, and system in the body causing sedentary dysfunction and accelerated death. The massive multifactorial nature of dysfunction caused by sedentarism means that just as food and reproduction remain as requirements for long-term continued human existence, physical activity is also a requirement to maximize health span and lifespan. The only valid scientific therapeutic approach to completely counter sedentary dysfunction is primary prevention with physical activity itself.

53 Acknowledgements

  1. Top of page
  2. Organization of Article
  3. Definitions
  4. Overview for Next Three Sections
  5. Summary of Daily Step Reductions from Antiquity
  6. History of Inactivity's Compromising Effects on Function and Health
  7. Cause Versus Treatment
  8. Mechanisms of Physical Inactivity and Activity Differ
  9. Gene-Exercise/Physical Inactivity Interactions
  10. Twin Studies: Modulation of Twin Phenotype by Physical Activity
  11. Variety of Training Types to Primarily Prevent Disease
  12. Diseasome of Physical Inactivity (35 Diseases/Conditions)
  13. Inactivity Accelerates Loss of Functional Capacities with Years of Life
  14. Prevention of Death by Primary Prevention of Physical Inactivity
  15. Metabolic Syndrome
  16. Presentation Strategy for Diseases Composing MS
  17. Obesity
  18. Inactivity Fosters Obese Comorbidities
  19. Insulin Sensitivity/Resistance
  20. Prediabetes
  21. Type 2 Diabetes
  22. Nonalcoholic Fatty Liver Disease
  23. Cardiovascular Diseases: All Types
  24. Presentation of Individual Cardiovascular Diseases
  25. Coronary Heart Disease
  26. Peripheral Arterial Disease
  27. Hypertension
  28. Stroke
  29. Congestive Heart Failure
  30. Known Mechanisms for CVD Risk Factors
  31. Deep Vein Thrombosis
  32. Cognitive Function
  33. Depression and Anxiety
  34. Bone (Osteoporosis)
  35. Osteoarthritis
  36. Balance
  37. Rheumatoid Arthritis
  38. Cancer
  39. Colon Cancer
  40. Breast Cancer
  41. Endometrial Cancer
  42. Activity Prevention of Female Reproductive Disorders
  43. Activity Prevention of Male Reproductive Disorders
  44. Pain
  45. Digestive Tract Diseases
  46. Chronic Respiratory Diseases
  47. Chronic Kidney Disease
  48. Clinical Significance of Physical Inactivity as One Cause of 35 Chronic Conditions
  49. Effectiveness of Drug Therapy for Simultaneous Primary Prevention of 35 Physical Inactivity Conditions
  50. Risk Factors Worsen Over 6 to 12 Months in RCTs
  51. Primary Prevention of Physical Inactivity: Childhood Developing Adult Disorders
  52. Public Policy
  53. Conclusion
  54. Acknowledgements
  55. References

The authors thank Jacob Brown, Marybeth Brown, Pam Hinton, Arthur Kramer, Thomas Meek, Scott Rector, Mike Roberts, Ron Terjung, John Thyfault, and Ryan Toedebusch for reviewing comments on specific sections of the article. The authors also thank Howard Wilson for constructing figures. This research was supported by anonymous gifts to FB. The article is dedicated to the continuing legacy of Charles M. Tipton and John O. Holloszy, who directly or indirectly touched the training of the authors.

References

  1. Top of page
  2. Organization of Article
  3. Definitions
  4. Overview for Next Three Sections
  5. Summary of Daily Step Reductions from Antiquity
  6. History of Inactivity's Compromising Effects on Function and Health
  7. Cause Versus Treatment
  8. Mechanisms of Physical Inactivity and Activity Differ
  9. Gene-Exercise/Physical Inactivity Interactions
  10. Twin Studies: Modulation of Twin Phenotype by Physical Activity
  11. Variety of Training Types to Primarily Prevent Disease
  12. Diseasome of Physical Inactivity (35 Diseases/Conditions)
  13. Inactivity Accelerates Loss of Functional Capacities with Years of Life
  14. Prevention of Death by Primary Prevention of Physical Inactivity
  15. Metabolic Syndrome
  16. Presentation Strategy for Diseases Composing MS
  17. Obesity
  18. Inactivity Fosters Obese Comorbidities
  19. Insulin Sensitivity/Resistance
  20. Prediabetes
  21. Type 2 Diabetes
  22. Nonalcoholic Fatty Liver Disease
  23. Cardiovascular Diseases: All Types
  24. Presentation of Individual Cardiovascular Diseases
  25. Coronary Heart Disease
  26. Peripheral Arterial Disease
  27. Hypertension
  28. Stroke
  29. Congestive Heart Failure
  30. Known Mechanisms for CVD Risk Factors
  31. Deep Vein Thrombosis
  32. Cognitive Function
  33. Depression and Anxiety
  34. Bone (Osteoporosis)
  35. Osteoarthritis
  36. Balance
  37. Rheumatoid Arthritis
  38. Cancer
  39. Colon Cancer
  40. Breast Cancer
  41. Endometrial Cancer
  42. Activity Prevention of Female Reproductive Disorders
  43. Activity Prevention of Male Reproductive Disorders
  44. Pain
  45. Digestive Tract Diseases
  46. Chronic Respiratory Diseases
  47. Chronic Kidney Disease
  48. Clinical Significance of Physical Inactivity as One Cause of 35 Chronic Conditions
  49. Effectiveness of Drug Therapy for Simultaneous Primary Prevention of 35 Physical Inactivity Conditions
  50. Risk Factors Worsen Over 6 to 12 Months in RCTs
  51. Primary Prevention of Physical Inactivity: Childhood Developing Adult Disorders
  52. Public Policy
  53. Conclusion
  54. Acknowledgements
  55. References
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